Spice Diode Modeling of Forward Overshoot & Reverse Recovery

[Jim Thompson]

Nothing like a PhD telling me something can't be done to get my solver
genes working double-time...

Over baby-back ribs at Firebirds this afternoon I realized how to
parameterize my method.

But all the information I have is from "peer-reviewed" semi-BS IEEE
papers.

Would someone be so kind as to take data on something common like a
1N914... forward overshoot and reverse recovery at various slew rates
and current levels?

Then I can fit a known object.

Thanks!

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

[John Larkin]

On Mon, 30 Jan 2017 17:37:44 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>Nothing like a PhD telling me something can't be done to get my solver
>genes working double-time...
>
>Over baby-back ribs at Firebirds this afternoon I realized how to
>parameterize my method.
>
>But all the information I have is from "peer-reviewed" semi-BS IEEE
>papers.
>
>Would someone be so kind as to take data on something common like a
>1N914... forward overshoot and reverse recovery at various slew rates
>and current levels?
>
>Then I can fit a known object.
>
>Thanks!
>
> ...Jim Thompson

I posted this previously:

https://dl.dropboxusercontent.com/u/53724080/Diode_TurnOn/1N914_a.JPG

https://dl.dropboxusercontent.com/u/53724080/Diode_TurnOn/1N914_b.JPG

https://dl.dropboxusercontent.com/u/53724080/Diode_TurnOn/1N914_c.JPG

https://dl.dropboxusercontent.com/u/53724080/Diode_TurnOn/1N914_d.JPG


That's a 1N914 from the middle of a 50-ohm transmission line to
ground. You can see the pulse drive level on the P400 display; that's
the unloaded generator output voltage... divide by 2 for the 50 ohm
load.

The diode is effectively driven by 25 ohms.

Generator rise time is about 1 ns.

In that last pic, you can see the diode holding up the falling edge of
the pulse for a couple of ns until it runs out of stored charge.

I wouldn't expect various "1N914" parts to be super similar.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[Jim Thompson]

What is the voltage step? That's not clear to me.

>
>In that last pic, you can see the diode holding up the falling edge of
>the pulse for a couple of ns until it runs out of stored charge.
>
>I wouldn't expect various "1N914" parts to be super similar.

I know :-( Been down that path many times ;-) Had to one time ban
the purchase of Motorola LM324's due to severe cross-over distortion
not seen in other vendor's parts.

[John Larkin]

On Mon, 30 Jan 2017 18:38:37 -0700, Jim Thompson

It's half the numbers seen on the P400 display. VH is pulse Vhigh, VL
is baseline Vlow. The VH is the unloaded pulse voltage, and the
generator is 50 ohms.



genVH(50r)-------------+---------------50R scope
|
A 1N914
K
|
gnd

[Jim Thompson]

On Mon, 30 Jan 2017 17:50:28 -0800, John Larkin

Thanks!

[Tim Wescott]

On Mon, 30 Jan 2017 17:37:44 -0700, Jim Thompson wrote:

> Nothing like a PhD telling me something can't be done to get my solver
> genes working double-time...
>
> Over baby-back ribs at Firebirds this afternoon I realized how to
> parameterize my method.
>
> But all the information I have is from "peer-reviewed" semi-BS IEEE
> papers.
>
> Would someone be so kind as to take data on something common like a
> 1N914... forward overshoot and reverse recovery at various slew rates
> and current levels?
>
> Then I can fit a known object.
>
> Thanks!
>
> ...Jim Thompson

What's the mechanism for forward overshoot? All those electrons and
holes are trying to decide between Uber and Lyft?

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

[Jim Thompson]

On Mon, 30 Jan 2017 20:32:40 -0600, Tim Wescott <t...@seemywebsite.com>
wrote:

>On Mon, 30 Jan 2017 17:37:44 -0700, Jim Thompson wrote:
>
>> Nothing like a PhD telling me something can't be done to get my solver
>> genes working double-time...
>>
>> Over baby-back ribs at Firebirds this afternoon I realized how to
>> parameterize my method.
>>
>> But all the information I have is from "peer-reviewed" semi-BS IEEE
>> papers.
>>
>> Would someone be so kind as to take data on something common like a
>> 1N914... forward overshoot and reverse recovery at various slew rates
>> and current levels?
>>
>> Then I can fit a known object.
>>
>> Thanks!
>>
>> ...Jim Thompson
>
>What's the mechanism for forward overshoot? All those electrons and
>holes are trying to decide between Uber and Lyft?

Probably ;-}

Actually it _is_ diffusion as Phil points out.

However that doesn't mean it's not modelable with Spice... as he
WRONGLY asserts.

[Clifford Heath]

Those graphs only show the resistive dimension of the impulses.
There will be a varying capacitance associated won't there,
which would change the shape of the impulse depending on the
impedance that the diode sees...?

Clifford Heath.

[John Larkin]

The P400 and the attenuator+scope are both clean 50 ohm things. The
diode is in the middle of a longish 50 ohm line, so it sees a very
ohmic 25 ohms.

The diode itself has a C-V curve, of course. And a little inductance.

Someone with more patience than me could do a more extensive
exploration of the 1N914 behavior.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[John Larkin]

On Mon, 30 Jan 2017 20:32:40 -0600, Tim Wescott <t...@seemywebsite.com>
wrote:

>On Mon, 30 Jan 2017 17:37:44 -0700, Jim Thompson wrote:
>
>> Nothing like a PhD telling me something can't be done to get my solver
>> genes working double-time...
>>
>> Over baby-back ribs at Firebirds this afternoon I realized how to
>> parameterize my method.
>>
>> But all the information I have is from "peer-reviewed" semi-BS IEEE
>> papers.
>>
>> Would someone be so kind as to take data on something common like a
>> 1N914... forward overshoot and reverse recovery at various slew rates
>> and current levels?
>>
>> Then I can fit a known object.
>>
>> Thanks!
>>
>> ...Jim Thompson
>
>What's the mechanism for forward overshoot? All those electrons and
>holes are trying to decide between Uber and Lyft?

Caught them napping.

We built a 2KV pulse generator that uses a silicon diode in
Grehkov/DSRD mode.

We applied 48 volts in the forward direction, and waited for the diode
to conduct. The current rose linearly to about 100 amps in maybe 80
ns, still at +48. Then we applied -400 through a small inductor. The
diode reverse conducted, basically shorted, for 50 ns or so as the
reverse current increased, then suddenly opened, when the stored
charge was depleted. The voltage twanged to -1KV for 2 or 3 ns, and we
doubled that with a transmission line.

The trick here is to forward bias the diode briefly, before the
carriers drift all over the place and pollute the junction. The HP1430
sampler (a 12 GHz oscilloscope in 1965) used a similar trick: forward
bias a step-recovery diode for a few ns to make the reverse snap
faster.

[Clifford Heath]

Yes. But even repeating the experiment with 2pF, or 2pF+ some R
parallel, would at least give some indication of the dynamic impedance.

Clifford Heath.

[Jim Thompson]

On Mon, 30 Jan 2017 17:33:05 -0800, John Larkin
<jjlark...@highlandtechnology.com> wrote:

John,

Could you repeat the experiment at different risetimes?

The theory (and gut) says the peak drops and "unsharpens" at slower
risetimes and eventually goes away...the rate at which it does this is
a measure of charge storage.

[gray_wolf]

All of my Motorola experiences have been bad. Small signal transistors in audio
stuff I was building in the '70s. A problem just waiting to happen. Arcade video
games in the '80s. Mostly TTL chips. Highest failure of all brands. Often a
quick fix was to replace any Motorola chips in the troubled area. Their 555
timer was notorious for that. I found some poor bonding from the die lead to the
output pins on some TO-3 devices in the power supply. This was on some high end
military stuff. Their RF comm stuff quality was generally fairly decent.




---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[John Larkin]

On Tue, 31 Jan 2017 12:00:43 -0600, gray_wolf <g_w...@nospam.com>
wrote:

Their microprocessors were great. 6800, 6802, 6803, 68K.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Jim Thompson]

On Mon, 30 Jan 2017 17:33:05 -0800, John Larkin
<jjlark...@highlandtechnology.com> wrote:

Here is a first-pass model without a whole lot of data...

<http://www.analog-innovations.com/DeviceModelsSubckts/D1N4148_FO_RRSpice_Model_2017-02-01_10-01-02.png>

for various rise/fall times...

** Analysis setup **
.tran 200ns 200ns 0 10ps
.STEP PARAM TRF LIST
+ 100ps 1ns 10ns 20ns 50ns

[John Larkin]

On Wed, 01 Feb 2017 10:06:33 -0700, Jim Thompson

That's not a model, it's a screenshot of some waveforms. As usual.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[Jim Thompson]

You and Phil need to grow up and cut the crap... I'm not going to
divulge what's in the model... unless you want to pay for a model >:-}
I'll post an encrypted model as soon as I figure out how to get a DOS
prompt in Win7 !@#$%^&*

[Jim Thompson]

On Mon, 30 Jan 2017 17:37:44 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>Nothing like a PhD telling me something can't be done to get my solver
>genes working double-time...
>
>Over baby-back ribs at Firebirds this afternoon I realized how to
>parameterize my method.
>
>But all the information I have is from "peer-reviewed" semi-BS IEEE
>papers.
>
>Would someone be so kind as to take data on something common like a
>1N914... forward overshoot and reverse recovery at various slew rates
>and current levels?
>
>Then I can fit a known object.
>
>Thanks!
>
> ...Jim Thompson

A first pass LTspice model:

Include everything that follows (except the sig) into a file named
D1N4148_FO_RR.lib...

* LTspice Encrypted File
*
* This encrypted file has been supplied by a 3rd
* party vendor that does not wish to publicize
* the technology used to implement this library.
*
* Permission is granted to use this file for
* simulations but not to reverse engineer its
* contents.
*
***********************************************************************************
**** SPICE MODELING by JIM THOMPSON,
http://www.analog-innovations.com/ © 2017 ****
***********************************************************************************
** Model is a first pass on modeling a 1N4148 diode forward overshoot
** based on limited datapoints
** Subcircuit Instantiation Node Order is:
** Anode Cathode
** Call as: Xyz Anode Cathode D1N4148_FO_RR
*****
* Begin:
67 61 A0 CD CF 70 B8 00 DC E2 F0 4C 54 18 A4 F5
BD 76 D5 34 E0 E5 47 78 2F 83 17 76 7A F0 F8 4B
19 5D 35 26 6C 4F 45 88 F1 D2 4B 52 06 55 B2 D8
21 78 11 E7 34 23 43 58 C2 CC 31 0E 52 35 D3 6A
A5 C6 63 FD C0 79 C6 16 DB 5E 75 72 13 B1 1E 3F
42 82 A6 39 A7 AF 3B 2A 0B 29 A5 00 CE 37 6D 26
03 61 A4 09 AD 5E 72 9C DA 02 9A C1 DC 7B F0 AE
55 B8 22 2D 70 7D 1E F0 EC E8 EA A0 18 47 C7 7B
3E 19 A8 3E 5A FD 54 28 9E 28 2A 17 4C 18 45 B5
E7 63 C1 D5 97 D3 B1 74 A5 FF 89 51 80 CB FC 12
DA 3D 85 77 61 07 9C D8 FA D4 41 54 33 6B 7B 84
70 A2 7B 1B 0B DF 76 9D A0 83 B6 62 A7 3F DA 9F
06 45 3C 4F D5 E7 AC 2E 84 3E 66 01 54 73 8A 0E
5B 9C C2 9F 11 21 65 11 9A EC 39 59 F3 6C F0 66
CF CA CA C5 58 CA 18 C9 F8 1D D0 2C 28 4F AC F1
7F 77 68 CC F6 77 BE A0 2A D3 42 29 3A A9 D8 B2
CF 9C 67 58 74 6D E3 CE AF 15 53 46 59 D5 94 B1
02 D3 6E 5C 8C C9 A2 AF 01 02 E2 46 3D AC 70 2C
8D B2 5B 81 BE 30 1B 7D 37 4F 9E 9A 48 EA 07 49
E7 E6 B8 DD 34 E0 1B B7 26 1E 6F F2 F8 FA B3 83
AA 34 60 43 3D D9 5B 22 DC 44 16 A4 E9 AA 44 21
5A F1 C0 9C BF 1C A8 22 AD CC C5 F0 29 C9 09 E0
C6 1F BE DB 78 28 82 5F 63 CA ED DB DD 54 18 05
D2 48 FE 31 D1 B6 D1 0F F7 DB 15 FF AC 16 3F A7
A1 49 7B FD DE C1 F3 88 FA 9B DC 79 4C F2 F5 19
72 40 9D BE 48 0B 48 DE 5A 67 02 D9 6A 90 6D FB
D9 80 FF 9F 82 FD 71 61 D8 1E 6E FE C3 84 E8 3F
7C 8E 90 02 6C 12 DD 6F 23 7C CF 90 F3 FD D3 E4
37 4C 93 31 19 7D 5E B5 C2 2F 53 26 9C 5F D4 35
79 9A 19 6C FC 18 78 62 FC E5 BF 9B A1 39 FA 84
17 76 E0 C6 B9 B3 C1 17 C4 B4 34 12 A0 CC FE 34
49 E8 17 CF DC 14 87 06 06 9B DD D1 47 0C 99 60
7B 1F F1 08 0C 54 85 38 10 7D D0 98 3D 94 13 70
34 52 91 17 5C 15 A1 C7 78 AC AD 1D 48 CA 08 7E
95 3F 30 01 CE 54 59 B2 35 42 70 2C 23 59 FB 46
AF 98 57 07 1A 8F C5 D1 0D 59 E4 F7 9D BA 33 06
C6 B2 54 EA 12 6C FC 0E AA 9F 80 B0 B2 C1 EC 42
92 C0 93 AE 14 9F 13 80 F9 19 A2 69 55 4E 99 1A
16 AB 63 55 E5 C0 5A 61 66 F8 B3 29 B9 69 5A 1B
E1 52 CA C9 9D B2 F4 39 89 15 AC BA 24 98 46 29
73 F1 34 14 B7 AB 41 97 58 EA D5 B4 49 89 6C E1
5D C6 1F 0D 9C 65 5B 54 90 3E 85 7C 16 8E A7 18
06 C6 9B 0E 64 43 A7 85 3A D4 A9 7B BE 6D BA A4
54 29 DF A0 EB 3B F4 45 4B FD E6 59 9E B7 E7 A8
DD DF 8A F8 9B B5 2A 1E 3E E7 0D FA 8E F3 AA 2A
5F 51 B4 4C 1B 91 3B 8B 31 DD A7 73 16 22 08 17
20 EC 9E BF F6 CD B6 01 58 71 9F C8 6F E2 7C EF
96 17 D5 FD 2B 31 3E DF FF 75 57 69 D3 D2 6E C4
E3 B2 CF 6C BD 18 54 D9 96 AC 10 33 B5 DC 5F 6D
37 BD D6 96 41 4A E1 A8 F7 23 D5 39 CC F0 8B 0F
82 44 27 84 A1 08 78 8D 18 79 DA D9 A7 75 97 84
28 DD 36 CA 95 6D 9B 28 2E 5B FF DF 59 C6 A1 57
EF 82 DC 30 11 94 65 EC 51 FF D5 B1 FD 29 EA C7
4B 7A 45 EA 92 37 61 D0 9B D2 E4 45 1F 73 E3 C8
3E DE FF 00 FC C1 36 8A FA 81 BB CB A9 B5 50 C3
35 8A C3 40 C0 0E 4D 75 AA 02 74 95 4C 00 0B 92
E4 09 1E 69 D2 E2 4D 3F 0D 7A 32 2B 2A CA BB 24
A2 6F B2 EB 25 1F 5A C8 BA FE 63 F2 3F BF DE F3
B7 E4 8B EE 29 94 98 DA D2 EA C2 81 BE C2 6F 03
E5 BE E7 11 80 3A D3 40 32 FD 08 0F A4 CA D6 66
BD B9 6F D2 DE 42 E5 75 C3 68 31 3C 29 53 E9 00
1C C5 E7 55 D3 DC 43 D2 F2 F6 D2 61 A7 38 7B 48
BB 97 6C 9E AF FD 2E 6A 3A 90 06 68 C8 E2 5E EB
D6 65 75 37 0A AA C7 F1 46 55 13 CC 60 82 E5 46
E3 9E 72 16 2C 9E 42 F7 F1 5B 41 E0 AE 82 EA 33
34 BE 79 60 B4 A9 C8 21 9F 8D 91 87 A8 AA 3E 37
9C E8 FB 82 F6 9D 91 94 2A 00 D0 0A 37 42 09 D6
DD 78 24 9A 3B 2F 05 8B 28 AB 91 77 94 31 F2 C2
5C 27 00 17 C0 16 4E 34 79 6D 95 CC 5A E4 64 EF
11 CF 2D 2F EA 06 40 82 71 08 45 FB 95 96 E1 69
57 41 A5 78 0E 93 14 D0 82 82 D0 98 1C 27 E4 86
D9 7F A0 8C 43 B0 AF E1 16 D5 8C 56 48 65 78 02
58 C0 7C 6F D4 22 65 F2 D9 63 FB 15 7E F7 97 83
1B C6 B2 8E 88 F4 1C D9 41 9F 06 F3 E7 52 16 4D
9F A2 48 72 02 2F DD 76 41 49 15 41 BF FB 94 05
DC 4A BC E8 A3 07 56 9B 15 6A F7 63 36 D6 81 48
2F DF 8B 95 29 A1 01 64 DA 2E 24 C8 73 07 CF 1E
3D 77 2E C4 1F A9 34 3E 1C 4A AB EC 59 52 0D E7
CD BE 5A 47 AD 13 94 90 F9 39 9F B6 CA 31 D2 9D
2A 6F 24 F9 AF 1F A9 01 28 6F F9 1C 42 65 4F 11
31 32 92 38 43 0D A7 81 3F ED 8F 4B 7B C3 13 AF
F7 8B 90 61 5D EF 02 0C 41 3F 0A D2 89 C8 05 B5
3D 7D AB 2B 3F 68 1E 9F 24 E5 5E E1 AF C9 89 47
7C 2A FF 7C 85 5C 66 7F 9C 2D A8 50 0E A2 85 8A
A9 D5 31 78 26 E0 76 9F E6 36 78 C5 EC A1 24 EC
5D 77 83 7C 1E DA 7F 40 72 31 37 1D 9C DA 04 D7
30 DD DF 0F 97 5F AF 2F 4E 7F 22 6F E7 C5 57 E1
4B C0 59 B1 81 8D 55 C3 9E D2 20 19 70 4E C4 CB
6A 2F 5F 49 C2 68 C5 38 EC 84 1B 48 76 F4 F8 14
AA 37 45 56 E3 3D 06 A4 20 89 C9 E6 3B 6D E8 52
C2 7B 84 CE 54 F8 6A FA D3 F9 76 3C 65 F0 8D 29
40 63 E0 80 58 1D 9B FD 6E 0A 86 D8 E2 FE 7F 52
41 DA 29 9A FA E5 8A C5 45 20 67 D6 D3 55 93 4F
C9 1A 70 A9 E8 94 14 F3 BC B6 CF BB D9 CA A5 68
26 23 2A BE 45 0D 48 DB 4F 38 C8 84 FA 38 75 15
18 41 1B 80 91 44 8C 0A 20 8E E4 7B 60 1C 31 D9
5C B3 D1 2B 3D DB DF 42 45 68 0B 7F B9 55 52 BC
0A CB 1E 93 E1 E2 65 F1 93 E4 17 DA 09 DA AE 94
D8 BE 20 8E 58 36 0F 3C 53 08 1B DE DD 59 87 8F
D2 93 7E 50 F6 E1 20 08 BE 48 F5 B9 71 40 B6 4B
FB 58 01 26 76 C4 42 25 02 2D 02 4B 01 6C 2C BD
50 E1 41 D6 49 9E DA 44 44 0F D6 E3 10 62 51 EE
9F B5 52 F9 17 45 CF 71 C5 2C 32 05 FB C8 0B F4
9E 2E 8D F8 4A 37 E5 08 B3 7F 6B C3 F2 82 75 31
0E 16 69 9A B5 D1 30 9D 07 83 03 47 5D 62 22 43
CD A6 8F 4B ED ED C3 34 6E 25 A0 F8 67 6F 2C 6C
55 2E 02 FF 31 10 7D 70 76 AB BA E3 43 70 C8 18
27 CF 7B 9B 61 B3 25 37 75 62 FC DB 29 80 FE 49
81 15 2C 16 65 E6 D1 BB F2 98 F0 5D 4A A9 32 AE
7A 6D BC 4D 8A 6D A1 62 E0 AB C8 0B D8 4D B3 22
E2 31 61 12 B7 57 97 8C C5 04 CF E5 41 DB 22 EF
FB 32 79 F6 DE 6C E5 63 A6 AF 0F 5D 18 F7 1D 32
8C AE A2 C6 CA 9E 2D F1 1D DB 62 2F D2 02 86 1F
D2 27 F7 52 C5 51 10 C4 B7 6F DE CD FA B3 EB 59
DE C2 09 FE B2 5B B8 71 E2 41 90 B5 F7 A2 00 6A
C5 03 CD 7F EE 48 5C 6C BC 68 50 21 9B A8 DA CC
B7 14 B4 18 5B 49 68 79 9D CF 68 E6 6F E1 37 B5
C8 92 18 91 0E 4F E6 F2 0F D6 AB 57 49 CD E9 16
D1 C3 CB 65 91 A6 32 72 14 53 E7 1C F7 50 7E B8
37 61 E9 83 0F C5 93 58 E2 6D 59 E8 7C 9A A5 4F
3A 09 D5 64 F0 2F 6D D4 EA 90 1B 84 CA 06 8E BF
ED 07 78 3D FD 80 1F 39 CD 68 1E 07 E8 E2 83 1F
B0 EA 8F 4A 48 23 26 49 91 A3 4A 2A 0F 82 B9 68
08 D1 48 04 03 A1 E4 A3 1B 28 FD 0C 11 AD A1 69
AB 63 20 34 D1 87 5E A2 34 61 CF 7F AA C8 18 10
61 F9 4D A9 E0 D9 DE 8A 2B 8F A6 1E 61 AB 28 00
3D EE 85 FC 0A 2C 7C 89 82 BC CF EF E2 3E E8 A8
6D FB 2D 75 31 0D DE ED 9F 15 C5 46 58 2C 17 F3
BB 59 6F 90 84 CB F8 01 7E C6 80 B1 AB 5E E6 5E
66 50 00 A5 AD A3 CC 98 2F E7 6E 31 17 C7 62 BD
0B 73 D6 41 0A 2E 06 5C DB 4D FC 67 F7 44 8D DA
E5 0B 7A C5 45 33 11 A6 39 AC 3B 46 EB 98 F2 A8
C7 DB 9C 0D 00 5D 46 DD 1A C2 DA 9F B6 21 E0 4C
10 C9 57 53 88 87 5E CD FE 01 2E AF 84 07 20 54
FB BE 84 0C 27 96 EB 25 12 FC C8 BE 35 60 AD 56
54 DA CF 6C 8E D0 0B 37 CE 78 E7 9E CD 8F BB 9D
19 42 85 CA C0 16 80 DB 84 14 25 86 9F 8B 9B 0E
9B 47 72 18 1B F4 6B 87 84 3D 83 70 61 88 82 E5
F2 0F AF D2 2F C9 20 E8 F3 C7 2A 7F 00 AB CC 46
A8 36 6D CA B7 73 A5 FC 63 6C 4B 8C BA 2C B6 AB
21 88 93 2B A7 5C 5C 9B 7F 43 BC 0C 2F FD 57 F5
3D A2 FB AB 20 7C 02 65 85 11 66 3D E8 48 67 17
0C 39 C0 80 1E E7 60 1D EB A2 A4 09 63 6D EA 5B
D1 3A 80 7C CB A3 BB 5E 78 1F F7 36 A2 E1 87 CF
6F A9 1C 03 2B B0 70 E5 9B 92 46 73 3C 93 DA 7D
E5 1B 8F 46 22 A8 11 70 7F F8 74 BE F0 C8 52 20
31 19 A4 86 A8 07 4E E4 0F 2D ED D8 61 11 E6 5D
* End 2231672352 423449410

[Tom Gardner]

On 01/02/17 18:28, Jim Thompson wrote:
> On Wed, 01 Feb 2017 09:48:54 -0800, John Larkin

>> That's not a model, it's a screenshot of some waveforms. As usual.
>
> You and Phil need to grow up and cut the crap... I'm not going to
> divulge what's in the model... unless you want to pay for a model >:-}
> I'll post an encrypted model as soon as I figure out how to get a DOS
> prompt in Win7 !@#$%^&*

That's your prerogative of course.

But the disagreement could easily be avoided by not calling
it a model in the first place.

[John Larkin]

On Wed, 01 Feb 2017 11:28:04 -0700, Jim Thompson

If you're not going to share what you know, all you are doing is
bragging about how smart you are, with no proof.

Encrypted model? Sounds paranoid to me.

--

John Larkin Highland Technology, Inc

[John Larkin]

On Wed, 01 Feb 2017 11:57:16 -0700, Jim Thompson

I should have encrypted my 1N914 waveform pics.

[Jim Thompson]

On Wed, 01 Feb 2017 11:02:18 -0800, John Larkin

How do we know if _your_ scope photos weren't rigged ?>:-}

>
>Encrypted model? Sounds paranoid to me.

Nope. I'm in the business of making money, just as you are... I only
give away the "free home demos" shown on the Device Models &
Subcircuits page of my website.

[Jim Thompson]

Show us how that is done >:-}

[John Larkin]

On Wed, 01 Feb 2017 12:07:41 -0700, Jim Thompson

Zip it with a password. Then I could pull a Thompson: "I have 1N914
forward recovery data, and you can't see it."

[JM]

There have been a lot of Spice diode models which account for charge
storage developed. Most if not all of them concentrate on PIN diodes
but I'm sure the same modeling techniques would apply to non PIN diodes.
Search in the IEEE journals related to power electronics if you're
interested (an example is http://ieeexplore.ieee.org/document/349750/).

[John Larkin]

On Wed, 01 Feb 2017 12:07:04 -0700, Jim Thompson

Because I am known to share stuff like this.

Hey, if I did fake it, then your model is crap. OK, I did fake it. All
your time has been wasted.

[Jim Thompson]

On Wed, 01 Feb 2017 19:14:17 +0000, JM <dontreply...@gmail.com>

wrote:

>> On Wed, 01 Feb 2017 10:06:33 -0700, Jim Thompson
>> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>

[snip]

>>>
>>> Here is a first-pass model without a whole lot of data...
>>>
>>> <http://www.analog-innovations.com/DeviceModelsSubckts/D1N4148_FO_RRSpice_Model_2017-02-01_10-01-02.png>
>>>
>>> for various rise/fall times...
>>>
>>> ** Analysis setup **
>>> .tran 200ns 200ns 0 10ps
>>> .STEP PARAM TRF LIST
>>> + 100ps 1ns 10ns 20ns 50ns
>>>
>>> ...Jim Thompson

[snip]

>>
>
>There have been a lot of Spice diode models which account for charge
>storage developed. Most if not all of them concentrate on PIN diodes
>but I'm sure the same modeling techniques would apply to non PIN diodes.
> Search in the IEEE journals related to power electronics if you're
>interested (an example is http://ieeexplore.ieee.org/document/349750/).

Papers aren't _my_ problem... I have several dozen on the subject. I
have developed a fairly simple modeling method that seems robust. All
I need is data from specific devices to test my method.

[Jim Thompson]

On Wed, 01 Feb 2017 11:15:27 -0800, John Larkin
<jjlark...@highlandtechnology.com> wrote:

>On Wed, 01 Feb 2017 12:07:04 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>

[snip]

>>>>>
>>>>>That's not a model, it's a screenshot of some waveforms. As usual.
>>>>
>>>>You and Phil need to grow up and cut the crap... I'm not going to
>>>>divulge what's in the model... unless you want to pay for a model >:-}
>>>>I'll post an encrypted model as soon as I figure out how to get a DOS
>>>>prompt in Win7 !@#$%^&*
>>>>
>>>> ...Jim Thompson
>>>
>>>If you're not going to share what you know, all you are doing is
>>>bragging about how smart you are, with no proof.
>>
>>How do we know if _your_ scope photos weren't rigged ?>:-}
>
>Because I am known to share stuff like this.

You shared photos, I shared screenshots. What's the difference?

>
>Hey, if I did fake it, then your model is crap. OK, I did fake it. All
>your time has been wasted.

No, my time wasn't wasted. That work was set aside last August
because I wasn't quite happy with it... so I pursued other items.

I find that approach often refreshes my mind, because, when I went
back to it, I realized a major simplification that escaped me
previously.

So I'm happy. Someone will provide data so I can compare measured
versus model, then I will publish; but I feel quite certain I've
cracked the nut.

[JM]

On 01/02/2017 19:20, Jim Thompson wrote:
> On Wed, 01 Feb 2017 19:14:17 +0000, JM <dontreply...@gmail.com>
> wrote:
>
>>> On Wed, 01 Feb 2017 10:06:33 -0700, Jim Thompson
>>> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>>
> [snip]
>>>>
>>>> Here is a first-pass model without a whole lot of data...
>>>>
>>>> <http://www.analog-innovations.com/DeviceModelsSubckts/D1N4148_FO_RRSpice_Model_2017-02-01_10-01-02.png>
>>>>
>>>> for various rise/fall times...
>>>>
>>>> ** Analysis setup **
>>>> .tran 200ns 200ns 0 10ps
>>>> .STEP PARAM TRF LIST
>>>> + 100ps 1ns 10ns 20ns 50ns
>>>>
>>>> ...Jim Thompson
> [snip]
>>>
>>
>> There have been a lot of Spice diode models which account for charge
>> storage developed. Most if not all of them concentrate on PIN diodes
>> but I'm sure the same modeling techniques would apply to non PIN diodes.
>> Search in the IEEE journals related to power electronics if you're
>> interested (an example is http://ieeexplore.ieee.org/document/349750/).
>
> Papers aren't _my_ problem... I have several dozen on the subject. I
> have developed a fairly simple modeling method that seems robust. All
> I need is data from specific devices to test my method.
>
> ...Jim Thompson
>

Here's some data courtesy of Bob Pease
https://www.dropbox.com/s/6s0o7j2rx59k5i8/pease.pdf?dl=0

[JM]

Which isn't of much use - just shows turn on.

[Jim Thompson]

On Wed, 01 Feb 2017 19:36:15 +0000, JM <dontreply...@gmail.com>

Thanks!

[John Larkin]

On Wed, 01 Feb 2017 12:27:10 -0700, Jim Thompson

<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Wed, 01 Feb 2017 11:15:27 -0800, John Larkin
><jjlark...@highlandtechnology.com> wrote:
>
>>On Wed, 01 Feb 2017 12:07:04 -0700, Jim Thompson
>><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>
>[snip]
>>>>>>
>>>>>>That's not a model, it's a screenshot of some waveforms. As usual.
>>>>>
>>>>>You and Phil need to grow up and cut the crap... I'm not going to
>>>>>divulge what's in the model... unless you want to pay for a model >:-}
>>>>>I'll post an encrypted model as soon as I figure out how to get a DOS
>>>>>prompt in Win7 !@#$%^&*
>>>>>
>>>>> ...Jim Thompson
>>>>
>>>>If you're not going to share what you know, all you are doing is
>>>>bragging about how smart you are, with no proof.
>>>
>>>How do we know if _your_ scope photos weren't rigged ?>:-}
>>
>>Because I am known to share stuff like this.
>
>You shared photos, I shared screenshots. What's the difference?

I shared all the info I had, and you are hiding and encripting what
you claim to know.

[Jim Thompson]

On Wed, 01 Feb 2017 14:45:07 -0800, John Larkin

<jjlark...@highlandtechnology.com> wrote:

>On Wed, 01 Feb 2017 12:27:10 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>On Wed, 01 Feb 2017 11:15:27 -0800, John Larkin
>><jjlark...@highlandtechnology.com> wrote:
>>
>>>On Wed, 01 Feb 2017 12:07:04 -0700, Jim Thompson
>>><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>>
>>[snip]
>>>>>>>
>>>>>>>That's not a model, it's a screenshot of some waveforms. As usual.
>>>>>>
>>>>>>You and Phil need to grow up and cut the crap... I'm not going to
>>>>>>divulge what's in the model... unless you want to pay for a model >:-}
>>>>>>I'll post an encrypted model as soon as I figure out how to get a DOS
>>>>>>prompt in Win7 !@#$%^&*
>>>>>>
>>>>>> ...Jim Thompson
>>>>>
>>>>>If you're not going to share what you know, all you are doing is
>>>>>bragging about how smart you are, with no proof.
>>>>
>>>>How do we know if _your_ scope photos weren't rigged ?>:-}
>>>
>>>Because I am known to share stuff like this.
>>
>>You shared photos, I shared screenshots. What's the difference?
>
>I shared all the info I had, and you are hiding and encripting what
>you claim to know.

I never claim anything I'm not sure of. And you're a horse's ass >:-}

[John Larkin]

On Wed, 01 Feb 2017 15:54:11 -0700, Jim Thompson

Well, helping you sure turns out to be a stupid thing to do.

[Phil Hobbs]

We aren't the ones doing the bragging at the moment, though, and an
encrypted model wouldn't prove anything, any more than the silly screen
shots do.

If your IP is that valuable, why take it to your grave?

And if money is your real reason for not posting the model, you have
your business plan all wrong. I published a major fraction of
everything I know about technology in a book that has been the
foundation of my consulting business.

If you were to write the H&H of modelling, you wouldn't have to be
looking for work, believe me. Folks would be better able to do the
routine jobs in house, but they'd send you the interesting ones.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

[Winfield Hill]

Phil Hobbs wrote...

>
> On 02/01/2017 01:28 PM, Jim Thompson wrote:
>>
>> You and Phil need to grow up and cut the crap...
>> I'm not going to divulge what's in the model...
>> unless you want to pay for a model >:-}
>

> If you were to write the H&H of modelling, you
> wouldn't have to be looking for work, believe me.
> Folks would be better able to do the routine
> jobs in house, but they'd send you the
> interesting ones.

I agree. And anyway, Jim makes his $$ and most
enjoys designing ICs. Nobody will be able to
match his skills at that, simply because he
might teach people how to model better. And as
you say, giving away secrets increases business.
Jim is getting along in years, and he should
start creating a serious legacy.


--
Thanks,
- Win

[Jim Thompson]

On Fri, 3 Feb 2017 09:26:03 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 02/01/2017 01:28 PM, Jim Thompson wrote:
>> On Wed, 01 Feb 2017 09:48:54 -0800, John Larkin
>> <jjla...@highlandtechnology.com> wrote:

[snip]

>>>
>>> That's not a model, it's a screenshot of some waveforms. As usual.
>>
>> You and Phil need to grow up and cut the crap... I'm not going to
>> divulge what's in the model... unless you want to pay for a model >:-}
>> I'll post an encrypted model as soon as I figure out how to get a DOS
>> prompt in Win7 !@#$%^&*
>>
>> ...Jim Thompson
>>
>
>We aren't the ones doing the bragging at the moment, though, and an
>encrypted model wouldn't prove anything, any more than the silly screen
>shots do.
>

[snip]

Running the encrypted model in LTspice and seeing the results wouldn't
prove anything ??

[Phil Hobbs]

On 02/03/2017 10:09 AM, Jim Thompson wrote:
> On Fri, 3 Feb 2017 09:26:03 -0500, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
>> On 02/01/2017 01:28 PM, Jim Thompson wrote:
>>> On Wed, 01 Feb 2017 09:48:54 -0800, John Larkin
>>> <jjla...@highlandtechnology.com> wrote:
>
> [snip]
>>>>
>>>> That's not a model, it's a screenshot of some waveforms. As
>>>> usual.
>>>
>>> You and Phil need to grow up and cut the crap... I'm not going to
>>> divulge what's in the model... unless you want to pay for a model
>>> >:-} I'll post an encrypted model as soon as I figure out how to
>>> get a DOS prompt in Win7 !@#$%^&* ...Jim Thompson
>>>
>>
>> We aren't the ones doing the bragging at the moment, though, and
>> an encrypted model wouldn't prove anything, any more than the
>> silly screen shots do.
>>
> [snip]
>
> Running the encrypted model in LTspice and seeing the results
> wouldn't prove anything ??

No, it wouldn't. Let me refresh your memory of what I actually wrote in
the "is there something wrong with PMOS" thread (with snippage restored):

> On 01/29/2017 10:59 AM, Jim Thompson wrote:
>> On Sun, 29 Jan 2017 04:43:37 -0800 (PST), pcdh...@gmail.com
>> wrote:
>>>>>>
>>>>>> There's generally nothing wrong with Spice... whatever the
>>>>>> flavor... IF the model is good.
>>>>
>>>>> There are two issues, I think. The first is (as you say) that the mfg
>>>>> needs to make good models if possible.
>>>>>
>>>>> The second is more of a SPICE limitation: the D() facility doesn't
>>>>> include diffusion delays, which makes it intrinsically incapable of
>>>>> accounting for V_F overshoot, and the MESFET facility doesn't model
>>>>> real device behaviour such as the aforementioned self-biasing of
>>>>> pHEMTs.
>>>>>
>>>>> The one is a modelling issue, but the second is an intrinsic
>>>>> limitation of the simulator.
>>>>>
>>>>> This is not to say that it can't be patched up, just that after N
>>>>> years we're still waiting. (Other more expensive tools may be better,
>>>>> of course.)


>>>>> The second is more of a SPICE limitation: the D() facility
>>>>> doesn't
>>>> include diffusion delays, which makes it intrinsically
>>>> incapable of accounting for V_F overshoot, and the MESFET
>>>> facility doesn't model real device behaviour such as the
>>>> aforementioned self-biasing of pHEMTs.
>>>
>>>> (1) Nonsense. It's quite feasible to write such a MODEL.
>>>
>>> I've asked about SPICE modelling the forward overshoot of diodes
>>> both here and in the Yahoo LTspice group, and heard in both
>>> places that the SPICE D() facility is too stupid to model it. If
>>> you can produce a model for a 1N4148 that overshoots to 1.4 V or
>>> so on turn-on (about par for a real unit), and exhibits the same
>>> variation with dI/dt as a real one, I'll happily concede your
>>> point.
>>>
>>> It won't be using just D(), though, that's for sure.
>>
>> You're evading my point. I said it is possible to write a proper
>> model. It just hasn't been done (properly) yet, though I've
>> developed a model that's pretty close, it's not _perfect_... I
>> strive for perfection so I'm still playing with it as time permits
>
> I'm not evading your point, I'm disagreeing with it. I claim that
> no such model exists, and you appear to agree. Your faith in SPICE
> is touching but provably wrong--it can't model everything without
> hacking the simulator code, not merely the models.
>
> For something whose behaviour is fairly simple and which has wide
> device-to-device variations, such as a diode with diffusion
> overshoot, you can probably cruft together some subcircuit model
> that gets vaguely into the ballpark, maybe using the transmission
> line model to account for time delays.
>
> It sure won't be just D() with parameters, though.

Which you eventually agreed with, and apparently have built such a model
for the simple step-excitation case.

I can't use it for anything because I don't use glass-package 1N914s any
more except in crufty breadboards, and can't adjust it to fit other
diodes.

And since it doesn't model actual diffusion behaviour, I have no reason
to suppose that it would work in more complicated and realistic
situations such as tone bursts in wideband noise.

If it were human-readable, I'd certainly read it, and might learn
something.

But it isn't, which makes it entirely uninteresting.

>
>>
>>>
>>>>>
>>>> The one is a modelling issue, but the second is an intrinsic
>>>> limitation of the simulator.
>>>
>>> (2) Nonsense. Refer to (1) above.
>>>
>>> SPICE is a pretty capable solver for largish sparse systems of
>>> nonlinear OD
>>
>> Yes. Pretty much as long as you can write an equation for it Spice
>> can solve it.
>>
>> ...Jim Thompson
>>
>
> No. Not transport equations, as I said, and there are lots of other
> examples of integral or integrodifferential equations. They're
> generally not reducible to systems of ODEs, because no ODE can be
> nonlocal, and so no solver limited to ODEs can handle them.
>
> You can't even write an ODE to describe a piece of coax from a
> circuits point of view--the SPICE transmission line isn't an ODE
> model, it's a special case, i.e. the simulator code has to be hacked
> up to support it.
>
> Cheers
>
> Phil Hobbs

You see here that what I'm disagreeing with is your blanket statement,
"Pretty much as long as you can write an equation for it Spice can solve
it." Which is provably false, as I said (and then proved).

Hacking together a subcircuit model that produces a similar curve is not
solving the actual 1-D transport equation.

[Jim Thompson]

On Fri, 3 Feb 2017 11:08:57 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

[snip]

>
>Hacking together a subcircuit model that produces a similar curve is not
>solving the actual 1-D transport equation.
>
>Cheers
>
>Phil Hobbs

Sorry. It's behavior is that of diffusion.

[bule...@columbus.rr.com]

I just love following these pissing contests

[Phil Hobbs]

On 02/03/2017 11:24 AM, Jim Thompson wrote:
> On Fri, 3 Feb 2017 11:08:57 -0500, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
> [snip]
>>
>> Hacking together a subcircuit model that produces a similar curve is not
>> solving the actual 1-D transport equation.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Sorry. It's behavior is that of diffusion.
>
> ...Jim Thompson
>

Prove it.

You might have put in a Gaussian someplace, but that's bolting together
special-case _solutions_, not solving the equation. Solving is when you
don't know the answer in advance.

And I'd bet ten dollars at even money that it won't do a good job on
tone bursts in wideband noise, or even on pulses with a lot of fast ringing.

[Phil Hobbs]

On 02/03/2017 11:26 AM, bule...@columbus.rr.com wrote:
> I just love following these pissing contests
>

Does that make you a weenie weenie? ;)

[Jim Thompson]

On Fri, 3 Feb 2017 11:33:47 -0500, Phil Hobbs

<pcdhSpamM...@electrooptical.net> wrote:

>On 02/03/2017 11:24 AM, Jim Thompson wrote:
>> On Fri, 3 Feb 2017 11:08:57 -0500, Phil Hobbs
>> <pcdhSpamM...@electrooptical.net> wrote:
>>
>> [snip]
>>>
>>> Hacking together a subcircuit model that produces a similar curve is not
>>> solving the actual 1-D transport equation.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> Sorry. It's behavior is that of diffusion.
>>
>> ...Jim Thompson
>>
>
>Prove it.

I do not have to "prove" anything to you. You are not an expert at
Spice behavioral modeling. I am.

[snip

I work on the basis that my customers are happy with the models I
provide, not on any basis that requires your approval.

Using terminology that you and Larkin are fond of invoking... do you
think your uninformed outbursts on this topic are helping your public
image ?>:-}

End of discussion.

[pcdh...@gmail.com]

>I work on the basis that my customers are happy with the models I
>provide, not on any basis that requires your approval.

Sure. I care about the truth, though, and am prepared to back up what I say with actual arguments. If I'm right, some folks might learn some things, and if I'm wrong, I learn some things too. So it's a win either way.

Cheers

Phil Hobbs

[Tom Gardner]

On 03/02/17 16:43, Jim Thompson wrote:
> On Fri, 3 Feb 2017 11:33:47 -0500, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
>> On 02/03/2017 11:24 AM, Jim Thompson wrote:
>>> On Fri, 3 Feb 2017 11:08:57 -0500, Phil Hobbs
>>> <pcdhSpamM...@electrooptical.net> wrote:
>>>
>>> [snip]
>>>>
>>>> Hacking together a subcircuit model that produces a similar curve is not
>>>> solving the actual 1-D transport equation.
>>>>
>>>> Cheers
>>>>
>>>> Phil Hobbs
>>>
>>> Sorry. It's behavior is that of diffusion.
>>>
>>> ...Jim Thompson
>>>
>>
>> Prove it.
>
> I do not have to "prove" anything to you. You are not an expert at
> Spice behavioral modeling. I am.
>
> [snip
>
> I work on the basis that my customers are happy with the models I
> provide, not on any basis that requires your approval.
>
> Using terminology that you and Larkin are fond of invoking... do you
> think your uninformed outbursts on this topic are helping your public
> image ?>:-}
>
> End of discussion.

All models are, by definition, incomplete representations.
A key point about any modelling is being able to understand
the *limits* of the model.

Encryption defeats that.

[Tom Gardner]

On 03/02/17 16:55, pcdh...@gmail.com wrote:
> If I'm right, some folks might learn some things,
> and if I'm wrong, I learn some things too. So it's
> a win either way.

That seems so obvious to me that I'm always surprised
when other people don't see things that way.

[Winfield Hill]

Jim Thompson wrote...

>
> I work on the basis that my customers are happy with the models
> I provide, not on any basis that requires your approval.

Are you primarily selling models as an end product,
or IC designs, in which you use your models to be
confidant of the result?


--
Thanks,
- Win

[Jim Thompson]

On 3 Feb 2017 09:20:19 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:

Right now my business is about 10/40/50 discrete/chip
design/behavioral modeling.

The behavioral models are for customer's chip designs that they wish
to keep the innards proprietary.

So they provide me with schematics and device-level netlists.

I exercise (exorcise sometimes ;-) them is PSpice and then simplify
the models to behavioral components that inhibit reverse engineering.

In particular my COSH(TANH(...)) OpAmp core model is virtually a
dead-on match to the device-level netlist, but totally useless to
anyone attempting to reverse engineer.

I'm cultivating the behavioral modeling end of my business because
it's fun (almost a puzzle-solving game ;-)... chip design, with my 55+
years of experience, has become pretty much a boring turn-the-crank
exercise... I've done it all before.

[John Larkin]

Only insecure people keep boasting about themselves. You are sounding
like Obama, lots of "I"s.

And what happened to "end of discussion" ?

[Jim Thompson]

On Fri, 03 Feb 2017 10:18:18 -0800, John Larkin
<jjlark...@highlandtechnology.com> wrote:

[snip]

>
>Only insecure people keep boasting about themselves. You are sounding
>like Obama, lots of "I"s.
>
>And what happened to "end of discussion" ?

Why don't you mind your own business? I was responding to Win's
questions? And you stuck your butt into the conversation uninvited.

As for "I"... I am the greatest >:-}

I don't know why I ever un-blacklisted you... back you go... your
contributions and comments are worthless.

[Jim Thompson]

On 3 Feb 2017 09:20:19 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:

I left out, in my previous answer...

I do, often, use behavioral modeling to mock up a system (SOC) and
check out the desired function before converting it to device-level.

Allowed me to catch, for a recent example, a video DC restorer that
clamped the sync tip to ground with a switch is NOT the way to go.

What a switch does is drops the input impedance, requiring a very low
source impedance to drag the clamped signal back positive... otherwise
video distortion.

The proper way is an active loop that uses a current pull-up to stop
the sync tip at the desired level.

[Cursitor Doom]

On Wed, 01 Feb 2017 15:37:34 -0800, John Larkin wrote:

>
> Well, helping you sure turns out to be a stupid thing to do.

Sigh. What a shame. For a minute there I thought you two were finally
going to get along.

[Tim Williams]

"Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message
news:yb2dna0H3qF7NwnF...@supernews.com...

> And since it doesn't model actual diffusion behaviour, I have no reason to
> suppose that it would work in more complicated and realistic situations
> such as tone bursts in wideband noise.

Phil,

Do you have any example data that illustrates the necessity of solving the
transport equation exactly?

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

[pcdh...@gmail.com]

>Phil,

>Do you have any example data that illustrates the necessity of solving the
>transport equation exactly?

>Tim

Well, JL's Grekhov diode pulser is a good one, as are normal SRDs. Even the lowly 1N914 will get charge density waves set up in it if you hit it with a fast ringy pulse, and the details of the response will depend on carrier diffusion.

If I wanted to really model photodetection accurately, I'd need to take into account the 2-1/2 D (i.e. cylindrically symmetric) diffusion problem of carrier transport and light absorption vs depth and wavelength. If the PD had only a single contact rather than a ring, it would be a full 3D problem. This matters a lot, because delay and bandwidth are functions of position, charge distribution, and lateral voltage drops.

And it all depends on the amount of reverse bias.

I've measured all those effects, but not in nearly adequate detail for modelling.

Of course if you know the analytic solution to enough special cases, you might possibly be able to cobble up something acceptably general for typical use cases. Optics and radar folks use the Geometric or Physical Theory of Diffraction (GTD/PTD), which works sort of like that. (Stealth technology is based on it, which is why the F-117A is all made of flat facets--you could simulate that on a 1970s computer.)

However, being a transport problem, carrier dynamics is way more complicated than vanilla electromagnetics--it's more like plasma physics. It's simpler because the ions can't move, but more complicated because of traps and defects and stuff. So doing the GTD thing would be hard.

Cheers

Phil Hobbs

[John Larkin]

On Tue, 31 Jan 2017 08:23:31 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Mon, 30 Jan 2017 17:33:05 -0800, John Larkin
><jjlark...@highlandtechnology.com> wrote:

>John,
>
>Could you repeat the experiment at different risetimes?

Sorry, that would be a lot of work, and I'd need a sub-ns highish
voltage pulse generator, which I don't have. The 1N914 isn't very
interesting, and I'd never use it in a nanosecond or picosecond
application.

Heck, we rarely use 1N914s at all!

Maybe I can kluge a resistor and a 1N914 onto the flipflop test rig
that I have set up. It can make a 3.3 or maybe 5 volt step, apparently
very fast. Barely possible.

>
>The theory (and gut) says the peak drops and "unsharpens" at slower
>risetimes and eventually goes away...the rate at which it does this is
>a measure of charge storage.

Sure, when the pulse risetime is much slower than the recombination
time, the recovery things vanish, and then LT Spice becomes accurate.

[pcdh...@gmail.com]

>>
>>The theory (and gut) says the peak drops and "unsharpens" at slower
>>risetimes and eventually goes away...the rate at which it does this is
>>a measure of charge storage.

>Sure, when the pulse risetime is much slower than the recombination
>time, the recovery things vanish, and then LT Spice becomes accurate.

I don't think it has to be that slow--in Si carriers can diffuse a long way before recombining.

Cheers

Phil Hobbs

[Jim Thompson]

On Fri, 3 Feb 2017 18:31:16 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

>"Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message
>news:yb2dna0H3qF7NwnF...@supernews.com...
>> And since it doesn't model actual diffusion behaviour, I have no reason to
>> suppose that it would work in more complicated and realistic situations
>> such as tone bursts in wideband noise.
>
>Phil,
>
>Do you have any example data that illustrates the necessity of solving the
>transport equation exactly?
>
>Tim

Particularly given the ability, in Spice, of creating a
voltage-and-current-and-charge variable capacitor ?>:-}

Then Spice can solve the so-called "transport equation".

[pcdh...@gmail.com]

>Particularly given the ability, in Spice, of creating a
>voltage-and-current-and-charge variable capacitor ?>:-}

>Then Spice can solve the so-called "transport equation".

I thought you didn't want to talk about it any more.

But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't.

Cheers

Phil Hobbs

[Jim Thompson]

Please explain _why_ you think Spice can't solve it. Stop thinking
explicit solutions... Spice is a numeric machine.

[Phil Hobbs]

On 02/03/2017 10:10 PM, Jim Thompson wrote:

>>> Particularly given the ability, in Spice, of creating a
>>> voltage-and-current-and-charge variable capacitor ?>:-}
>>
>>> Then Spice can solve the so-called "transport equation".
>>
>> I thought you didn't want to talk about it any more.
>>
>> But you're entirely wrong once again. Any sort of
>> capacitor--nonlinear, time varying, whatever you like--still obeys
>> an ODE. Transport doesn't.

> Please explain _why_ you think Spice can't solve it. Stop thinking
> explicit solutions... Spice is a numeric machine.

A particular kind of numeric machine, but not a universal one, however
clever a modeller you may be.

SPICE is a pretty capable solver for sparse systems of nonlinear,
coupled, ordinary differential equations, and suffices for most circuit
purposes as well as a large class of other problems that can be reduced
to such a system.

A general system of N variables leads to an NxN matrix that has to be
solved on each time step. The effort required goes as N**3, which gets
old fast.

Sparse systems have many fewer nonzero elements, typically just a few
near the main diagonal. For instance, FDTD codes such as my EM
simulator lead to a heptadiagonal matrix (seven entries per row,
corresponding to the current volume element and six nearest neighbours.
That kind is pretty simple to solve, in theory, taking a few times N
operations per time step. (FDTD is a bit slower because you have to
shrink the time step as you refine the mesh, so it goes like N**(4/3).)

However, circuits aren't that regular, leading to sparse systems whose
nonzero entries can be anywhere, but which typically have no more than
five or so connections per node, which helps a lot.

Like all (or nearly all) solvers for systems like that, SPICE uses
iterative methods that take more steps but avoid filling in the zero
entries. These methods aren't guaranteed to converge unless the system
is numerically stable and the initial guess is sufficiently close, which
is why SPICE needs all that help with convergence.

It's a good tool all round, but it can only solve ODE systems unless the
code is hacked up to add features (such as transmission lines).

Transport problems such as gas motion are not in general expressible as
systems of ODEs. Classical nonequilibrium gas transport is governed by
the Boltzmann equation (see e.g.
<https://en.wikipedia.org/wiki/Boltzmann_equation>) which is an
irreducible integrodifferential equation.

Carrier motion is more complicated because there are two kinds of
carriers that move and recombine according to quantum rules, and because
electric and magnetic fields are coupled to the phase space density, but
it's still a set of coupled integrodifferential equations, and so can't
be solved by SPICE.

The difference is basically that integrodifferential equations have a
lot of internal state that ODEs don't, and they can be nonlocal in time,
i.e. the result of the next step doesn't depend merely on the
observables from the previous step.

For instance, a transmission line in SPICE is also an integral equation,
because what comes out one end is a delayed replica of what went in the
other end. You can't express that as a differential equation, because
it has internal state that isn't visible at the terminals. You have to
express it as a convolution integral with a shifted Dirac delta function
(perhaps with a high frequency cutoff).

ODE systems have a very rich set of possible responses, so (as you know
better than I) it's possible to dream up ways to mimic the behaviour of
many IDEs with SPICE models in restricted situations. For instance, if
you know that the transmission line will only have pulses going into it,
you can use a delayed source to mimic that.

However, because these models don't correctly represent the internal
state of the solutions of the transport equation, a change in conditions
is very likely to make the mimicry fail. Sending charge density waves
into a 1N914 by hitting it with a step with a big 2-GHz ring is an
example. A model based only on the response to a clean step is unlikely
to get that right, because it has no way of expressing the wave
behaviour, which will have excursions in both density and momentum.

Transmission lines are sufficiently important that it's worth hacking up
the solver to handle them as a special case, which fortunately is quite
simple. Transport is another kettle of fish entirely.

[Tim Williams]

<pcdh...@gmail.com> wrote in message
news:5e74e19b-3950-45dc...@googlegroups.com...

> Well, JL's Grekhov diode pulser is a good one, as are normal SRDs. Even
> the lowly 1N914 will get charge density waves set up in it if you hit it
> with a fast ringy pulse, and the details of the response will depend on
> carrier diffusion.

Okay, but who does that?

I can safely say I have never seen a circuit expose 1N914s to microwaves.
And anyone who claimed to do so would be seen as retarded.

I see zero value in creating that model.


A much more useful situation is an ordinary power rectifier, where you hit
it with a "fast ringy pulse" that's produced from a switching inverter.
"Fast" in quotes because it's maybe tens of nanoseconds at the fastest.

In that regime, transport looks like series inductance, but it's nonlinear
and non-conservative. An R||L can crudely replicate part of the behavior
(like voltage overshoot), but doesn't help with reverse recovery and losses.

There are millions of inverters out there. This is a high value target. It
would be fantastic to have an accurate measure of power dissipation, and
dynamics, in a simulation of a real, practical circuit.

In the extreme case, one could simulate the electromagnetic and thermal
response of the entire device, before ever ordering a prototype.

That's a model that has real value.


Phil, are you not motivated by value? Surely there's nothing worse than
cooking up some (academically or computationally) amazing toy, and having it
go nowhere because it's some obscure, useless bit of math that no one needs.

It sounds like you /are/ motivated by value, because accurate PD models
would be directly useful to you, and of competitive advantage if you had
them.


So I don't get your obsession with analytical accuracy. You're being a
useless dick about it. If all your PhD has to say is "can't be done", then
would you please step out of this conversation while the engineers discuss
the "well what if..."?

Please do correct me if I'm wrong about any of these things: the value of an
analytical 1N914 model, or a rectifier, or PD, or the reasons for your
obstinance.

Cheers,

[Jim Thompson]

On Sat, 4 Feb 2017 01:50:22 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

[snip]

>
>However, because these models don't correctly represent the internal
>state of the solutions of the transport equation, a change in conditions
>is very likely to make the mimicry fail. Sending charge density waves
>into a 1N914 by hitting it with a step with a big 2-GHz ring is an
>example. A model based only on the response to a clean step is unlikely
>to get that right, because it has no way of expressing the wave
>behaviour, which will have excursions in both density and momentum.
>

[snip]

What does the real device do under such circumstances?

Win's post, while at a much lower frequency, would indicate nothing
visible.

Besides, forward overshoot and reverse recovery are of most importance
to the power supply application, not something with a "2-GHz ring".

I have 55 "learned" papers on Spice modeling forward overshoot and
reverse recovery.

Their models are grotesque complex because they aren't Spice
aficionados, they're equation bangers ;-)

However their models do match the measured behavior quite closely.

But so does mine at 11 lines total... a much simpler approach using
controlled sources (that allow equations in their templates ;-)

I _will_ ultimately publish. What I seek yet is a way to simply plug
in numbers from a datasheet and automatically parameterize the model's
equations. Right now I have to manually twiddle coefficients until I
get a fit.

Of note, once fit, the model behavior _does_ track slew rate _and_
peak current values.

[Jim Thompson]

On Sat, 4 Feb 2017 09:08:44 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

[snip]

>
>
>So I don't get your obsession with analytical accuracy. You're being a
>useless dick about it. If all your PhD has to say is "can't be done", then
>would you please step out of this conversation while the engineers discuss
>the "well what if..."?
>
>Please do correct me if I'm wrong about any of these things: the value of an
>analytical 1N914 model, or a rectifier, or PD, or the reasons for your
>obstinance.
>
>Cheers,
>
>Tim

Sno-o-o-o-ort >:-}

[Winfield Hill]

Jim Thompson wrote...

>
> Win's post, while at a much lower frequency,
> would indicate nothing visible.

My post? Do you mean John's scope traces post?


--
Thanks,
- Win

[Jim Thompson]

On 4 Feb 2017 07:42:56 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:

>Jim Thompson wrote...
>>
>> Win's post, while at a much lower frequency,
>> would indicate nothing visible.
>
> My post? Do you mean John's scope traces post?

I guess you didn't post it, but someone posted a link to your
experiment forward biasing a 1N914 at various rates.

I'll see if I can re-find that link.

[Jim Thompson]

On 3 Feb 2017 06:36:07 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:


[snip]

> Jim is getting along in years...

As are you ;-)

[John Larkin]

On Fri, 3 Feb 2017 17:26:34 -0800 (PST), pcdh...@gmail.com wrote:

>>Phil,
>
>>Do you have any example data that illustrates the necessity of solving the
>>transport equation exactly?
>
>>Tim
>
>Well, JL's Grekhov diode pulser is a good one, as are normal SRDs. Even the lowly 1N914 will get charge density waves set up in it if you hit it with a fast ringy pulse, and the details of the response will depend on carrier diffusion.

A model for the Grehkov effect would only be useful if one were
designing the doping profile on purpose. But the DSRS application is
obscure and it's more practical to just test available power diodes,
of unknown guts, for behavior. The best Grehkov diode that I've found
was the c-b junction of a power transistor, based on no more theory
than a vague hunch.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

[John Larkin]

On Fri, 03 Feb 2017 20:10:37 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Fri, 3 Feb 2017 18:24:38 -0800 (PST), pcdh...@gmail.com wrote:
>
>>>Particularly given the ability, in Spice, of creating a
>>>voltage-and-current-and-charge variable capacitor ?>:-}
>>
>>>Then Spice can solve the so-called "transport equation".
>>
>>I thought you didn't want to talk about it any more.
>>
>>But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't.
>>
>>Cheers
>>
>>Phil Hobbs
>>
>
>Please explain _why_ you think Spice can't solve it. Stop thinking
>explicit solutions... Spice is a numeric machine.
>
>

...Jim Thompson

And what happened to "end of discussion" ?

[Jim Thompson]

On 4 Feb 2017 07:42:56 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:

>Jim Thompson wrote...
>>
>> Win's post, while at a much lower frequency,
>> would indicate nothing visible.
>
> My post? Do you mean John's scope traces post?

My error, it was an experiment by Pease, not by you...

<https://www.dropbox.com/s/6s0o7j2rx59k5i8/pease.pdf?dl=0>

[John Larkin]

On Sat, 04 Feb 2017 09:06:30 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On 3 Feb 2017 06:36:07 -0800, Winfield Hill <hi...@rowland.harvard.edu>
>wrote:
>
>
>[snip]
>
>> Jim is getting along in years...
>
>As are you ;-)
>
> ...Jim Thompson

AoE will be used and remembered, by the millions, for some years to
come.

Are you passing your IC design skills on to anyone? I try to teach my
kids everything that I know, and give away all but our few crown
jewels, publically and privately. (And none is encrypted!)

When people call with a problem for which we don't have a product or
time to address their problem, we help them if we can. Maybe a sketch,
a link, or we suggest another source. It's nice to do and
coincidentally it's good business.

[Phil Hobbs]

On 02/04/2017 10:08 AM, Tim Williams wrote:
> <pcdh...@gmail.com> wrote in message
> news:5e74e19b-3950-45dc...@googlegroups.com...
>> Well, JL's Grekhov diode pulser is a good one, as are normal SRDs. Even
>> the lowly 1N914 will get charge density waves set up in it if you hit it
>> with a fast ringy pulse, and the details of the response will depend on
>> carrier diffusion.
>
> Okay, but who does that?
>
> I can safely say I have never seen a circuit expose 1N914s to
> microwaves. And anyone who claimed to do so would be seen as retarded.
>
> I see zero value in creating that model.

So don't. I'm not going to either. I was asked for situations where
SPICE would fail, and that's one. SRDs are another, as I said. Lots of
people do expose those to microwaves, after all. (Improving a SRD
tripler was one of my very first engineering jobs, back in 1981-2. I
did it with a pencil, quite literally.)

Simulating a 10-wavelength piece of coax is still another, except that
SPICE has been hacked up to deal with that specific transport problem.
I invite you to try doing that with LCs and see how many it takes.

In other words, if SPICE is all you need for your work, terrific, but
there's a big world out there.

>
>
> A much more useful situation is an ordinary power rectifier, where you
> hit it with a "fast ringy pulse" that's produced from a switching
> inverter. "Fast" in quotes because it's maybe tens of nanoseconds at the
> fastest.
>
> In that regime, transport looks like series inductance, but it's
> nonlinear and non-conservative. An R||L can crudely replicate part of
> the behavior (like voltage overshoot), but doesn't help with reverse
> recovery and losses.
>
> There are millions of inverters out there. This is a high value
> target. It would be fantastic to have an accurate measure of power
> dissipation, and dynamics, in a simulation of a real, practical circuit.

It sounds like we're in violent agreement now. Weird.

>
> In the extreme case, one could simulate the electromagnetic and thermal
> response of the entire device, before ever ordering a prototype.

But not in SPICE.

>
> That's a model that has real value.
>
>
> Phil, are you not motivated by value? Surely there's nothing worse than
> cooking up some (academically or computationally) amazing toy, and
> having it go nowhere because it's some obscure, useless bit of math that
> no one needs.

Tim, with all due respect, that's a very stupid question. And you seem
to have an odd definition of "nobody", i.e. "Not Tim Williams".

>
> It sounds like you /are/ motivated by value, because accurate PD models
> would be directly useful to you, and of competitive advantage if you had
> them.
>
>
> So I don't get your obsession with analytical accuracy. You're being a
> useless dick about it. If all your PhD has to say is "can't be done",
> then would you please step out of this conversation while the engineers
> discuss the "well what if..."?

If not thinking that circuit design is all there is to engineering is
"being a useless dick", I plead guilty.

However, I'm pretty sure I've worked in more areas of technology than
you have, so I have a different view. One example.

In order to do my antenna coupled tunnel junction silicon photonics
work, I had to write my own clusterized optimizing EM simulator, which I
still use and which is superior in many respects to anything you can buy
at any price. (It's called POEMS, for "Programmable Optimizing
Electromagnetic Simulator, and you can read the manual on my web site if
you're interested.)

It was fun, but it took most of a year, and I wouldn't have done it
unless I had to--at the time there were zero full 3D EM simulators that
could optimize device geometry, and I needed one. (I started with a big
wrapper script around Berkeley TEMPEST, but that ran out of stooch
pretty fast because it was single-threaded, which is why I had to do my
own clusterized FDTD engine.) It needed to support free-electron
metals, because I was using gold and silver antennas. Vanilla FDTD
can't do those because they have an epsilon that is very nearly a
negative real number, and the Yee (FDTD) algorithm blows up. You have
to add state, usually an auxiliary differential equation, to each volume
element containing such materials. Transport could be put in the same
sort of way if I needed it.

What I got out of it was the opportunity to develop a completely new
optical interconnection technology that nobody thought would work--until
it did. You tell me if that's value or not.

> Please do correct me if I'm wrong about any of these things: the value
> of an analytical 1N914 model, or a rectifier, or PD, or the reasons for
> your obstinance.

I mentioned the 1N914 because that's what Jim's behavioural model is
trying to represent. Please tell my why you ignored the SRD example.

And where have I said anything about analytical accuracy?

I'm talking about the general tendency of any sort of unphysical fitted
model (numerical or analytical) to become inaccurate rapidly once you
exceed some neighbourhood of where the fitting occurred. This isn't
specifically a SPICE problem--it happens all over, and usually doesn't
announce itself. If there's one thing I hate, it's reasonable-looking
wrong answers.

My post was a response to Jim's question about exactly why SPICE
couldn't solve transport problems such as carrier dynamics in silicon.

And merely having a settled opinion that isn't the same as yours is not
being obstinate. Neither of us is 18 years old.

[Phil Hobbs]

Sure, one doesn't do that sort of thing for no reason. The
photodetection example I gave upthread is maybe more apropos--you really
do want to use that to guide the design of the photodiode.

I have a device from Excelitas whose propagation delay varies no more
than 30 ps over the full width of the active area. Some C-V
measurements showed that it has an APD-style structure inside, i.e. a
buried layer of high doping that generates a huge electric field when
you deplete it fully. Bolting a transport capability onto SPICE would
allow optimizing that and trading it off against capacitance and series
resistance, and seeing what the whole circuit would do. I'd give my eye
teeth to be able to do that.

[John Larkin]

On Sat, 04 Feb 2017 09:41:48 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On 4 Feb 2017 07:42:56 -0800, Winfield Hill <hi...@rowland.harvard.edu>
>wrote:
>
>>Jim Thompson wrote...
>>>
>>> Win's post, while at a much lower frequency,
>>> would indicate nothing visible.
>>
>> My post? Do you mean John's scope traces post?
>
>My error, it was an experiment by Pease, not by you...
>
><https://www.dropbox.com/s/6s0o7j2rx59k5i8/pease.pdf?dl=0>
>
> ...Jim Thompson

At 1 mA, the rise is slow and capacitances dominate, so he didn't get
much overshoot. Slam it harder, and you can forward-bias a 1N914 to
lots of volts. Pease's observed change of overshoot with rep rate
suggests some very slow diffusions going on.

https://dl.dropboxusercontent.com/u/53724080/Parts/Diode_TurnOn/1N914_c.JPG

I've run power diodes at 48 volts forward bias, for a while.

We used (or, actually, couldn't use) some laser diodes that acted like
they had big inductors or something inside. A sneak-up-on-it drive
pulse would create a big voltage overshoot and a long wait for light
to come out. If it was pulsed at maybe 1 MHz, the effect disappeared.
One of the layers was acting like a slow PIN diode in series with the
rest.

[John Larkin]

On Wed, 01 Feb 2017 12:20:43 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Wed, 01 Feb 2017 19:14:17 +0000, JM <dontreply...@gmail.com>
>wrote:
>
>>> On Wed, 01 Feb 2017 10:06:33 -0700, Jim Thompson
>>> <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>>>
>[snip]
>>>>
>>>> Here is a first-pass model without a whole lot of data...
>>>>
>>>> <http://www.analog-innovations.com/DeviceModelsSubckts/D1N4148_FO_RRSpice_Model_2017-02-01_10-01-02.png>
>>>>
>>>> for various rise/fall times...
>>>>
>>>> ** Analysis setup **
>>>> .tran 200ns 200ns 0 10ps
>>>> .STEP PARAM TRF LIST
>>>> + 100ps 1ns 10ns 20ns 50ns
>>>>
>>>> ...Jim Thompson
>[snip]
>>>
>>
>>There have been a lot of Spice diode models which account for charge
>>storage developed. Most if not all of them concentrate on PIN diodes
>>but I'm sure the same modeling techniques would apply to non PIN diodes.
>> Search in the IEEE journals related to power electronics if you're
>>interested (an example is http://ieeexplore.ieee.org/document/349750/).
>
>Papers aren't _my_ problem... I have several dozen on the subject. I
>have developed a fairly simple modeling method that seems robust. All
>I need is data from specific devices to test my method.
>
> ...Jim Thompson

Don't use mine. It was all faked.

[Jim Thompson]

On Sat, 4 Feb 2017 09:08:44 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

[snip]
>

>There are millions of inverters out there. This is a high value target. It
>would be fantastic to have an accurate measure of power dissipation, and
>dynamics, in a simulation of a real, practical circuit.
>
>In the extreme case, one could simulate the electromagnetic and thermal
>response of the entire device, before ever ordering a prototype.
>
>That's a model that has real value.
>
>

[snip]

They exist.

For example, Infineon BSC014NE2LSU Spice model includes an elaborate
thermal section.

Unfortunately it was written by "equation bangers" with a lot of IF
statements... a total disaster, so I'm trying to decipher it and
remove the thermal crap so I can manage to do a transient analysis
that doesn't hang :-(

[John Larkin]

On Sat, 4 Feb 2017 12:38:56 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 02/04/2017 11:07 AM, John Larkin wrote:
>> On Fri, 3 Feb 2017 17:26:34 -0800 (PST), pcdh...@gmail.com wrote:
>>
>>>> Phil,
>>>
>>>> Do you have any example data that illustrates the necessity of
>>>> solving the transport equation exactly?
>>>
>>>> Tim
>>>
>>> Well, JL's Grekhov diode pulser is a good one, as are normal SRDs.
>>> Even the lowly 1N914 will get charge density waves set up in it if
>>> you hit it with a fast ringy pulse, and the details of the response
>>> will depend on carrier diffusion.
>
>>
>> A model for the Grehkov effect would only be useful if one were
>> designing the doping profile on purpose. But the DSRS application is
>> obscure and it's more practical to just test available power diodes,
>> of unknown guts, for behavior. The best Grehkov diode that I've
>> found was the c-b junction of a power transistor, based on no more
>> theory than a vague hunch.
>
>Sure, one doesn't do that sort of thing for no reason. The
>photodetection example I gave upthread is maybe more apropos--you really
>do want to use that to guide the design of the photodiode.

Actually, the hunch was guided by the observation that diffused
non-epitaxial junctions have a better chance of blundering into a good
doping profile. Boff discovered the step-recovery effect like that,
lucky diffusion profile. Theorists then followed up and optimized it.

Epitaxial junctions don't seem to snap.

>
>I have a device from Excelitas whose propagation delay varies no more
>than 30 ps over the full width of the active area. Some C-V
>measurements showed that it has an APD-style structure inside, i.e. a
>buried layer of high doping that generates a huge electric field when
>you deplete it fully. Bolting a transport capability onto SPICE would
>allow optimizing that and trading it off against capacitance and series
>resistance, and seeing what the whole circuit would do. I'd give my eye
>teeth to be able to do that.
>
>Cheers
>
>Phil Hobbs

The PD case would involve inputting 3D doping profiles and anode
metalization patterns and such, hardly Spice stuff. I guess that,
knowing all that, you could do a better Spice model. Do you think that
Spice model would benefit from some sort of diffusion element, hacked
like the transmission line? I just kluge up something that behaves
like the real thing over a narrow operating range.

[John Larkin]

On Sat, 4 Feb 2017 12:33:47 -0500, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 02/04/2017 10:08 AM, Tim Williams wrote:
>> <pcdh...@gmail.com> wrote in message
>> news:5e74e19b-3950-45dc...@googlegroups.com...
>>> Well, JL's Grekhov diode pulser is a good one, as are normal SRDs. Even
>>> the lowly 1N914 will get charge density waves set up in it if you hit it
>>> with a fast ringy pulse, and the details of the response will depend on
>>> carrier diffusion.
>>
>> Okay, but who does that?
>>
>> I can safely say I have never seen a circuit expose 1N914s to
>> microwaves. And anyone who claimed to do so would be seen as retarded.
>>
>> I see zero value in creating that model.
>
>So don't. I'm not going to either. I was asked for situations where
>SPICE would fail, and that's one. SRDs are another, as I said. Lots of
>people do expose those to microwaves, after all. (Improving a SRD
>tripler was one of my very first engineering jobs, back in 1981-2. I
>did it with a pencil, quite literally.)
>
>Simulating a 10-wavelength piece of coax is still another, except that
>SPICE has been hacked up to deal with that specific transport problem.
>I invite you to try doing that with LCs and see how many it takes.

Hacked or not, LT Spice does transmission lines well, and it's a lot
of fun and education to play with them.

One gotcha: it ignores the impedance of the low side, like a coax
shield, to the universe, so it behaves as if there is an ideal
transformer inside the line. That can be useful in itself.

[George Herold]

Phil, (I feel like I'm barley touching bottom math-wise, so be gentle.)
But can't you sorta solve transport equations by putting in initial
conditions, turn the differentials into differences and then step
the solution along, with a small enough time step. ?
George H.

[Winfield Hill]

Jim Thompson wrote...

> Tim Williams wrote:
>
>[snip]
>>
>> There are millions of inverters out there. This is a
>> high value target. It would be fantastic to have an
>> accurate measure of power dissipation, and dynamics,
>> in a simulation of a real, practical circuit.
>

> They exist.
> For example, Infineon BSC014NE2LSU Spice model includes
> an elaborate thermal section.
>

> Unfortunately it was written by "equation bangers" ...

Manufacturer's models aren't of much use beyond the
millisecond territory, because they don't / can't
include one's heat-sink and PCB thermal information.


--
Thanks,
- Win

[Jim Thompson]

On Sat, 04 Feb 2017 11:14:24 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Sat, 4 Feb 2017 09:08:44 -0600, "Tim Williams"
><tiw...@seventransistorlabs.com> wrote:
>
>[snip]
>>
>>There are millions of inverters out there. This is a high value target. It
>>would be fantastic to have an accurate measure of power dissipation, and
>>dynamics, in a simulation of a real, practical circuit.
>>
>>In the extreme case, one could simulate the electromagnetic and thermal
>>response of the entire device, before ever ordering a prototype.
>>
>>That's a model that has real value.
>>
>>
>[snip]
>
>They exist.
>
>For example, Infineon BSC014NE2LSU Spice model includes an elaborate
>thermal section.
>
>Unfortunately it was written by "equation bangers" with a lot of IF
>statements... a total disaster, so I'm trying to decipher it and
>remove the thermal crap so I can manage to do a transient analysis
>that doesn't hang :-(
>
> ...Jim Thompson

Ugh! Removed the thermal crap and discover that the core model is
LEVEL=1. How the frick do designers get reliable results with such
crap?

[George Herold]

Oops Phil, just ignore that... I hadn't gotten to your latter
reply to JT.

Geo

[Phil Hobbs]

I've used it fairly often, most recently in that $2 diode sampler, where
I had a 50-ps stub with a mismatched load to help shape the sampling
pulse. Being able to twiddle that in SPICE was a great
help--breadboarding with 0402s in mid air is hard. (Chester W and
prototyped it like that back in December--worked great.)

I'm really not knocking LTspice, which is a really nice and very capable
program that I use all the time. It just isn't the One True Numerical
Solution To Everything, even for circuits.

[John Larkin]

On 4 Feb 2017 10:31:36 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:

I like to run a realtime junction temperature simulation, analog or
digital, to protect mosfets. That lets one safely push them a lot
harder than a simple current or foldback limiter.

My usual model is scaled power dissipation driving a 1st order lag,
added to heatsink temperature. Tau's are typically in the 100
millisecond range. We calibrate the model by destructive tests.

Here's an analog mosfet power dissipation computer:

https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Soar_Calc.jpg

[Winfield Hill]

John Larkin wrote...

>
> Here's an analog mosfet power dissipation computer:
>https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/Soar_Calc.jpg

Yes, that's a powerful technique, and it you feed
it to the right kind of computing circuit, or a
micro ADC + program, you can protect the MOSFET.


--
Thanks,
- Win

[Jim Thompson]

On 4 Feb 2017 11:38:01 -0800, Winfield Hill <hi...@rowland.harvard.edu>
wrote:

You can also implement the ideal equivalent to that in Spice, add a
heatsink model, and do more things than the crap thermal stuff
presently included in the present models.

I've even implemented SOA display for MOS devices with PSpice (*)
macros, including hot electron problem coverage for very short channel
devices.

(*) Probably doable also in LTspice, I just haven't tried.

[Tim Williams]

"Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message
news:uMCdnTLjxP3VjQvF...@supernews.com...

> So don't. I'm not going to either. I was asked for situations where
> SPICE would fail, and that's one.

Great!

I don't see anyone arguing that SPICE has doesn't have limitations*.

*Jim might not appreciate the distributed-state property of your examples,
like TLs or transport. But that's his problem.

Feel free to call that battle a success. ;-)

> SRDs are another, as I said. Lots of
> people do expose those to microwaves, after all. (Improving a SRD tripler
> was one of my very first engineering jobs, back in 1981-2. I did it with
> a pencil, quite literally.)

Okay, cool.

So, how far can you take it?

Suppose a model can be created, and that it has a finite number of free
variables. (Whether approximating it in SPICE, or in an environment that
can actually solve transport phenomena.)

How much data do you need to fix all those parameters?

And how many of those can be read off the datasheet, or measured easily?

Without this critical information, your model is again just a curiosity.
You have the means to solve it, but no data to enter into the solver.


I suspect this information will be hard to come by, for SRDs. So, though it
might be a valuable application, can a usefully accurate model even be
created (in any environment)?

(And that's without discussing the PCB, where even trace widths and corners
matter to these picosecond signals.)

> In other words, if SPICE is all you need for your work, terrific, but
> there's a big world out there.

Tons of things have been simulated successfully with SPICE. That hasn't
stopped anyone, despite their models being trivial, utterly unrealistic
toys. :)

>> Phil, are you not motivated by value? Surely there's nothing worse than
>> cooking up some (academically or computationally) amazing toy, and
>> having it go nowhere because it's some obscure, useless bit of math that
>> no one needs.
>
> Tim, with all due respect, that's a very stupid question. And you seem to
> have an odd definition of "nobody", i.e. "Not Tim Williams".

That wasn't phrased very well on my part -- I wasn't referring to transport
(or the simulator you made!), but "some amazing toy (...) that no one
needs".


As long as you've brought it up -- "nobody" is a rather peculiar word. Its
meaning seems plain, but it's used most often to mean: "no one that I know
of". Language is shitty like that...

> In order to do my antenna coupled tunnel junction silicon photonics work,
> I had to write my own clusterized optimizing EM simulator, which I
> still use and which is superior in many respects to anything you can buy
> at any price. (It's called POEMS, for "Programmable Optimizing
> Electromagnetic Simulator, and you can read the manual on my web site if
> you're interested.)

I've read about it before -- pretty amazing stuff, Phil!

> I mentioned the 1N914 because that's what Jim's behavioural model is
> trying to represent. Please tell my why you ignored the SRD example.

Duly explained above (I suspect the physics-bits aren't well enough
documented to make it reasonable to fit, even when a solution can be
constructed).

So, you have no concerns about the ability to model a 1N914 at limited
dI/dt..? Yes it would almost certainly be easier with transport, but if
that's not in your toolkit, how would you do it?

There seem to be two behaviors of interest here: SRD behavior, and the
lossy-inductor regime.

Are these behaviors so deeply inseparable, from the underlying phenomenon of
charge diffusion, that one must solve for that, to have any reasonable
success at modeling just one or the other?

That seems to be what you're saying, in regards to the 1N914. Or if not,
then... please, share the model?! :D

> And where have I said anything about analytical accuracy?
>
> I'm talking about the general tendency of any sort of unphysical fitted
> model (numerical or analytical) to become inaccurate rapidly once you
> exceed some neighbourhood of where the fitting occurred. This isn't
> specifically a SPICE problem--it happens all over, and usually doesn't
> announce itself. If there's one thing I hate, it's reasonable-looking
> wrong answers.

That's why you put the assumptions in the liner notes!

If there's one thing I hate, it's models that don't even say what their
limits are!

Trivial example: PCB trace impedance calculators that dutifully spit out
negative impedances. Ferrite bead models are awful, too, and never specify
their useful range. Let alone nonlinearity.

A diode, modeled with forward recovery, with the attached note saying
"invalid above 1000 A/us", would be lovely!

Anyone who is sufficiently experienced at SPICE to appreciate the bounds of
their models, should be grateful to see something like that. Maybe the
limit precludes accurate analysis of a particular application (say if a
particular monolithic switcher accidentally spits out SRD pulses..), but it
will still be applicable to others (like a more relaxed inverter that has
enough stray inductance to limit dI/dt).

[Clifford Heath]

On 05/02/17 07:03, Tim Williams wrote:
> "Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message
> news:uMCdnTLjxP3VjQvF...@supernews.com...

>> SRDs are another, as I said. Lots of
>> people do expose those to microwaves, after all. (Improving a SRD
>> tripler was one of my very first engineering jobs, back in 1981-2. I
>> did it with a pencil, quite literally.)
>
> Okay, cool.
>
> So, how far can you take it?
>
> Suppose a model can be created, and that it has a finite number of free
> variables. (Whether approximating it in SPICE, or in an environment
> that can actually solve transport phenomena.)
>
> How much data do you need to fix all those parameters?
>
> And how many of those can be read off the datasheet, or measured easily?
>
> Without this critical information, your model is again just a curiosity.
> You have the means to solve it, but no data to enter into the solver.
>
> I suspect this information will be hard to come by, for SRDs. So,
> though it might be a valuable application, can a usefully accurate model
> even be created (in any environment)?

Perhaps if there was a model and solver that could use that data,
then there would be more incentive to provide it. Chicken, egg.

Clifford Heath

[Jim Thompson]

On Fri, 3 Feb 2017 18:31:16 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

>"Phil Hobbs" <pcdhSpamM...@electrooptical.net> wrote in message

>news:yb2dna0H3qF7NwnF...@supernews.com...
>> And since it doesn't model actual diffusion behaviour, I have no reason to
>> suppose that it would work in more complicated and realistic situations
>> such as tone bursts in wideband noise.

>
>Phil,
>
>Do you have any example data that illustrates the necessity of solving the
>transport equation exactly?
>
>Tim

I have retrieved a few SRD papers.

Looks like I can even model "transport" in Spice.

Nothing is impossible to model with Spice.

Watch this space >:-}

[pcdh...@gmail.com]

>Nothing is impossible to model with Spice.
>Watch this space >:-}

Wow, between that and the Donald, I may OD on popcorn. ;)

Cheers

Phil Hobbs

[Jim Thompson]

I did that last night... and now I am suffering some intestinal
discomfort.... I really shouldn't eat popcorn... seems the wine turns
it to concrete :-(

But you do indeed need to watch this space ;-)

[bill....@ieee.org]

On Sunday, February 5, 2017 at 2:27:10 AM UTC+11, Jim Thompson wrote:
> On Sat, 4 Feb 2017 01:50:22 -0500, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
> [snip]
> >
> >However, because these models don't correctly represent the internal
> >state of the solutions of the transport equation, a change in conditions
> >is very likely to make the mimicry fail. Sending charge density waves
> >into a 1N914 by hitting it with a step with a big 2-GHz ring is an
> >example. A model based only on the response to a clean step is unlikely
> >to get that right, because it has no way of expressing the wave
> >behaviour, which will have excursions in both density and momentum.
> >
> [snip]
>
> What does the real device do under such circumstances?

>
> Win's post, while at a much lower frequency, would indicate nothing
> visible.
>

> Besides, forward overshoot and reverse recovery are of most importance
> to the power supply application, not something with a "2-GHz ring".
>
> I have 55 "learned" papers on Spice modeling forward overshoot and
> reverse recovery.
>
> Their models are grotesque complex because they aren't Spice
> aficionados, they're equation bangers ;-)
>
> However their models do match the measured behavior quite closely.
>
> But so does mine at 11 lines total... a much simpler approach using
> controlled sources (that allow equations in their templates ;-)
>
> I _will_ ultimately publish. What I seek yet is a way to simply plug
> in numbers from a datasheet and automatically parameterize the model's
> equations. Right now I have to manually twiddle coefficients until I
> get a fit.\

Sounds like a job for a nonlinear multi-parameter least squares curve fitting procedure.

My Ph.D. project used Fletcher-Powell - the Fortran package solution available from the computation department was based on Marquardt but couldn't be shoe-horned into my software, so I had to write my own, and the Fletcher-Powell approach seemed more suitable for my particular problem.

https://en.wikipedia.org/wiki/Davidon%E2%80%93Fletcher%E2%80%93Powell_formula

https://en.wikipedia.org/wiki/Non-linear_least_squares

> Of note, once fit, the model behavior _does_ track slew rate _and_
> peak current values.

Working within a restricted parameter space, a model doesn't have to be physically realistic to work. Physically realistic models can be expected to hold up better when used outside the operating range within which the model was fitted.

--
Bill Sloman, Sydney

[John Larkin]

On Sat, 04 Feb 2017 17:32:26 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Sat, 4 Feb 2017 16:29:42 -0800 (PST), pcdh...@gmail.com wrote:
>
>>>Nothing is impossible to model with Spice.
>>>Watch this space >:-}
>>
>>Wow, between that and the Donald, I may OD on popcorn. ;)
>>
>>Cheers
>>
>>Phil Hobbs
>
>I did that last night... and now I am suffering some intestinal
>discomfort.... I really shouldn't eat popcorn... seems the wine turns
>it to concrete :-(
>
>But you do indeed need to watch this space ;-)
>
> ...Jim Thompson

Too much popcorn will lacerate your plumbing. Blood.

[Jim Thompson]

On Sat, 4 Feb 2017 09:08:44 -0600, "Tim Williams"
<tiw...@seventransistorlabs.com> wrote:

[snip]

[replying to Phil Hobbs]...

>
>So I don't get your obsession with analytical accuracy. You're being a
>useless dick about it. If all your PhD has to say is "can't be done", then
>would you please step out of this conversation while the engineers discuss
>the "well what if..."?
>

>Please do correct me if I'm wrong about any of these things: the value of an
>analytical 1N914 model, or a rectifier, or PD, or the reasons for your
>obstinance.
>

>Cheers,
>
>Tim

Over dinner last night I was musing about Spice models, my diode model
covering forward overshoot and the resulting hysteria amongst the
"elite".

It struck me that most of the lurkers on this group are engineers.

All that an engineer cares about in regard to a Spice model is that
it's terminal behavior be the same as the real device behaves in his
system/PCB.

The engineer doesn't give a damn whether the model duplicates the
actual physics of the device or not, only that it performs properly.

I would argue that attempting to model a device following the complete
physics of a device produces a cumbersome, difficult to converge and
slow-to-simulate model.

I have 55 "learned"/peer-reviewed papers in my
forward-overshoot/reverse-recovery research file that demonstrate my
point ;-)

I would point out, for instance, that the Spice model for a bipolar
device is not a model that conveys the actual physics of the device,
but a simulatablely-tractable approximation.

The elitists amongst us would insist that a proper model can't be
created unless it "solves" the underlying physics equations.

That is nonsense.

In my musing, not even committed to paper yet, just rolling the
function around in my head, I realized that a controlled charge
accumulation, metered release could easily model the sacred SRD... no
solution of a transport equation involved.

When I posted the waveforms of my forward recovery model, the resident
pompous asshole reared his ugly head and pronounced, "...only
waveforms".

Sonnuva gun, I do believe that's what engineers want to see on their
simulator and their 'scope... not a scrolling useless paper extolling
that the physics equation has been solved.

Lastly, I think many people here are using LTspice, and the elitists
and the resident pompous asshole hang their hats on the results...

I would suggest you check out the accuracy of the resident Spice
models... all based on nearly ideal approximations to emphasize
simulation speed... not accuracy.

HTH >:-}

[bill....@ieee.org]

On Monday, February 6, 2017 at 3:07:19 AM UTC+11, Jim Thompson wrote:
> On Sat, 4 Feb 2017 09:08:44 -0600, "Tim Williams"
> <tiw...@seventransistorlabs.com> wrote:

[snip]

> It struck me that most of the lurkers on this group are engineers.
>
> All that an engineer cares about in regard to a Spice model is that
> it's terminal behavior be the same as the real device behaves in his
> system/PCB.
>
> The engineer doesn't give a damn whether the model duplicates the
> actual physics of the device or not, only that it performs properly.
>
> I would argue that attempting to model a device following the complete
> physics of a device produces a cumbersome, difficult to converge and
> slow-to-simulate model.

Not necessarily.

> I have 55 "learned"/peer-reviewed papers in my
> forward-overshoot/reverse-recovery research file that demonstrate my
> point ;-)
>
> I would point out, for instance, that the Spice model for a bipolar
> device is not a model that conveys the actual physics of the device,
> but a simulatablely-tractable approximation.

Gummel-Poon doesn't capture inverted transistor behaviour that makes Baxandall class-D oscillators "squeg" when built with bipolar transistors and a too-big feed inductor.

> The elitists amongst us would insist that a proper model can't be
> created unless it "solves" the underlying physics equations.
>
> That is nonsense.

It is. A proper model must respect the underlying physics as much as it can - and the underlying physics is often a royal route to a good model - but - as the Gummel-Poon example makes clear - an imperfect model can often be very useful.

It's nice if it's imperfections are spelled out, as they rarely are.

> In my musing, not even committed to paper yet, just rolling the
> function around in my head, I realized that a controlled charge
> accumulation, metered release could easily model the sacred SRD... no
> solution of a transport equation involved.

Phil Hobbs did spell out why this might not work as well as you like to think, and might have given you a clue to an approach that might work better.

> When I posted the waveforms of my forward recovery model, the resident
> pompous asshole reared his ugly head and pronounced, "...only
> waveforms".

Waveforms are the integrated output of complex processes. A waveform has one value at one moment. The process that generates the waveform has several variables all of which are varying with time.

> Sonnuva gun, I do believe that's what engineers want to see on their
> simulator and their 'scope... not a scrolling useless paper extolling
> that the physics equation has been solved.

That's what they want to see. This doesn't mean that it's what they ought to be looking for.

> Lastly, I think many people here are using LTspice, and the elitists
> and the resident pompous asshole hang their hats on the results...

We all know that LTSpice outputs can be misleading. The trick is to know when, where and why.

> I would suggest you check out the accuracy of the resident Spice
> models... all based on nearly ideal approximations to emphasize
> simulation speed... not accuracy.

Gummell-Poon is pretty accurate, where it works. VBIC - which LTSpice will run - is supposed to be better, if you can get the parameters for a specific part. Semiconductor manufacturers treat them as trade secrets.

--
Bill Sloman, Sydney

[Jim Thompson]

On Sun, 5 Feb 2017 19:01:04 -0800 (PST), bill....@ieee.org wrote:

>On Monday, February 6, 2017 at 3:07:19 AM UTC+11, Jim Thompson wrote:

[snip]

>
>> I would suggest you check out the accuracy of the resident Spice
>> models... all based on nearly ideal approximations to emphasize
>> simulation speed... not accuracy.
>
>Gummell-Poon is pretty accurate, where it works. VBIC - which LTSpice will run - is supposed to be better, if you can get the parameters for a specific part. Semiconductor manufacturers treat them as trade secrets.

Most of the foundries I deal with (that have processes with bipolar
devices) _do_ provide VBIC models (PSpice runs them as well).

Unfortunately most _discrete_ device manufacturers don't provide
adequate models, if they provide any at all.

[Jim Thompson]

On Mon, 06 Feb 2017 10:16:43 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Sun, 5 Feb 2017 19:01:04 -0800 (PST), bill....@ieee.org wrote:
>
>>On Monday, February 6, 2017 at 3:07:19 AM UTC+11, Jim Thompson wrote:
>
>[snip]
>>
>>> I would suggest you check out the accuracy of the resident Spice
>>> models... all based on nearly ideal approximations to emphasize
>>> simulation speed... not accuracy.
>>
>>Gummell-Poon is pretty accurate, where it works. VBIC - which LTSpice will run - is supposed to be better, if you can get the parameters for a specific part. Semiconductor manufacturers treat them as trade secrets.
>
>Most of the foundries I deal with (that have processes with bipolar
>devices) _do_ provide VBIC models (PSpice runs them as well).
>
>Unfortunately most _discrete_ device manufacturers don't provide
>adequate models, if they provide any at all.
>
> ...Jim Thompson

You missed that my point was about LTspice... LTspice's default models
are gross simplifications.

[evelyn....@gmail.com]

https://support.google.com/photos/thread/115943?msgid=115982

[John Larkin]

On Sun, 13 May 2018 21:12:13 -0700 (PDT), evelyn....@gmail.com
wrote:

>https://support.google.com/photos/thread/115943?msgid=115982

"Update required"

Update of what?

Google is evil. Post pix to Dropbox or something.

I recently made a pulse generator using a Cree SiC fet. Their Spice
model assumes zero forward recovery time of the substrate diode.
Wrong.

[Jim Thompson]

On Mon, 14 May 2018 07:12:36 -0700, John Larkin
<jjla...@highlandtechnology.com> wrote:

>On Sun, 13 May 2018 21:12:13 -0700 (PDT), evelyn....@gmail.com
>wrote:
>
>>https://support.google.com/photos/thread/115943?msgid=115982
>
>"Update required"
>
>Update of what?
>
>Google is evil. Post pix to Dropbox or something.
>
>I recently made a pulse generator using a Cree SiC fet. Their Spice
>model assumes zero forward recovery time of the substrate diode.
>Wrong.

Spice Modeling of forward AND reverse recovery is difficult due to
lack of real data. Thus my original post...

Message-ID: <tomv8clnib23d5t57...@4ax.com>

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions,
by understanding what nature is hiding.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie