Simple pulse stretcher

George Herold

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Mar 7, 2013, 1:21:33 PM3/7/13

to

Hi guys, I need a little digital pulse stretcher. I've got pulses
that are 5ns to 25ns in width, and I'd like to bump them all up to all
be at least 10ns. I've got a few spare 74HC14 inverters. I was
thinking of just feeding one through a diode followed by an R/C to
ground. Any other ways? There might be an extra AND gate too.
(not my circuit so I'm not quite sure.)

Thanks

George H.
(and who ordered the second t in stretcher)

Jim Thompson

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Mar 7, 2013, 1:33:29 PM3/7/13

to

Joerg

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Mar 7, 2013, 1:34:31 PM3/7/13

to

George Herold wrote:
> Hi guys, I need a little digital pulse stretcher. I've got pulses
> that are 5ns to 25ns in width, and I'd like to bump them all up to all
> be at least 10ns. I've got a few spare 74HC14 inverters. I was
> thinking of just feeding one through a diode followed by an R/C to
> ground. Any other ways? There might be an extra AND gate too.
> (not my circuit so I'm not quite sure.)
>

The diode thing is what I usually do. But 10nsec through a 74HC14? Now
that's a strrrrretch.

--
Regards, Joerg

http://www.analogconsultants.com/

George Herold

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Mar 7, 2013, 2:01:25 PM3/7/13

to

On Mar 7, 1:33 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-

Web-Site.com> wrote:
> On Thu, 7 Mar 2013 10:21:33 -0800 (PST), George Herold
>

> <gher...@teachspin.com> wrote:
> >Hi guys, I need a little digital pulse stretcher. I've got pulses
> >that are 5ns to 25ns in width, and I'd like to bump them all up to all
> >be at least 10ns. I've got a few spare 74HC14 inverters. I was
> >thinking of just feeding one through a diode followed by an R/C to
> >ground. Any other ways? There might be an extra AND gate too.
> >(not my circuit so I'm not quite sure.)
>
> >Thanks
>
> >George H.
> >(and who ordered the second t in stretcher)
>
> Isn't 10ns width just a wee-bit tight for 74HC parts?
>
> ...Jim Thompson
> --
> | James E.Thompson | mens |
> | Analog Innovations | et |
> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
> | Phoenix, Arizona 85048 Skype: Contacts Only | |
> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat |

> | E-mail Icon athttp://www.analog-innovations.com| 1962 |

>
> I love to cook with wine. Sometimes I even put it in the food.

OK, maybe I should stretch to 20 ns.

George H.

George Herold

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Mar 7, 2013, 2:06:04 PM3/7/13

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OK thanks, I'll do 20ns then.

George H.

Joerg

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Mar 7, 2013, 2:07:15 PM3/7/13

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Still a bit of a stretch but if you need pulses this short there are
faster versions of the HC14.

John Larkin

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Mar 7, 2013, 2:48:31 PM3/7/13

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On Thu, 7 Mar 2013 10:21:33 -0800 (PST), George Herold <ghe...@teachspin.com>
wrote:

Why not use a one-shot? HC123 or the faster Tiny version of same, SN74LVC1G123.

The other way is to set a D-flop that resets itself. That can be a lot faster.

--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

Jim Thompson

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Mar 7, 2013, 3:01:57 PM3/7/13

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| E-mail Icon at http://www.analog-innovations.com | 1962 |

Jim Thompson

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Mar 7, 2013, 3:03:15 PM3/7/13

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What I was driving at was how can the 74HC do the stretch in the first
place... reliably. Though I think I possibly see a way.

| E-mail Icon at http://www.analog-innovations.com | 1962 |

Vladimir Vassilevsky

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Mar 7, 2013, 3:12:45 PM3/7/13

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Something like this:

http://www.abvolt.com/misc/pulse_stretch.jpg

You got the idea.

/*
Placeholder for banal comments
*/

Vladimir Vassilevsky
DSP and Mixed Signal Designs
www.abvolt.com

George Herold

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Mar 7, 2013, 3:36:39 PM3/7/13

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Yeah I was thinking of something like that too. The diode thing was
an easy 'hack' and seems to be working just fine. (I stuck in 10k
and 10pF and have about a 50ns minimum pulse.) Life is good.

George H.

John Larkin

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Mar 7, 2013, 3:42:52 PM3/7/13

to

On Thu, 07 Mar 2013 14:12:45 -0600, Vladimir Vassilevsky <nos...@nowhere.com>
wrote:

>On 3/7/2013 12:21 PM, George Herold wrote:
>> Hi guys, I need a little digital pulse stretcher. I've got pulses
>> that are 5ns to 25ns in width, and I'd like to bump them all up to all
>> be at least 10ns. I've got a few spare 74HC14 inverters. I was
>> thinking of just feeding one through a diode followed by an R/C to
>> ground. Any other ways? There might be an extra AND gate too.
>> (not my circuit so I'm not quite sure.)
>>
>> Thanks
>>
>> George H.
>> (and who ordered the second t in stretcher)
>>
>
>Something like this:
>
>http://www.abvolt.com/misc/pulse_stretch.jpg
>
>You got the idea.
>

>/*
>Placeholder for banal comments

I think that can double-glitch the output if you tease the input width just
right.

>*/

John Fields

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Mar 7, 2013, 3:43:40 PM3/7/13

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On Thu, 7 Mar 2013 10:21:33 -0800 (PST), George Herold

---
"Pulse stretcher" implies that the leading edge of the source pulse
should be presented at the input of the load simultaneously with its
generation, and that its fall should occur after the desired delay.

The former is, of course, unrealizable, while the latter is easy.

How much delay can you tolerate between the generation of the leading
edge of the source pulse and its presentation to the load?

--
JF

John Larkin

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Mar 7, 2013, 3:56:22 PM3/7/13

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On Thu, 7 Mar 2013 11:01:25 -0800 (PST), George Herold <ghe...@teachspin.com>
wrote:

The diode+RC thing is perfectly feasible with an HC14, likely at 20 ns out and
certainly at 30.

A bit of inductance in series with the R would be interesting.

Here's a variation on Vlad's circuit:

https://dl.dropbox.com/u/53724080/SED/Stretcher.JPG

Joerg

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Mar 7, 2013, 3:56:59 PM3/7/13

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Diode plus Schmitt is the better solution. The main reason is that doing
it with piped-in gates relies on their prop delays. I have seen that
blow up in production when people did it. All it takes is one or more
manufacturers improving a semiconductor process, things become faster,
suddenly the fix ain't working no more. Or only sometimes. Datasheets
typically do not specify a guaranteed lower limit on prop delay. For
example, there is no entry for it in the "min" column for the 74HC14
from TI:

http://www.ti.com/lit/ds/symlink/sn74hc14.pdf

John Larkin

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Mar 7, 2013, 3:59:53 PM3/7/13

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On Thu, 7 Mar 2013 12:36:39 -0800 (PST), George Herold <ghe...@teachspin.com>
wrote:

Just make sure the schottky has low c, a couple of pF or less.

John Fields

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Mar 7, 2013, 4:08:49 PM3/7/13

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---
You've still got the initial gate delay from input to output, and the
prop delay through the buffers isn't exactly precise...

--
JF

John Larkin

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Mar 7, 2013, 4:32:22 PM3/7/13

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On Thu, 07 Mar 2013 15:08:49 -0600, John Fields <jfi...@austininstruments.com>
wrote:

That's pretty much unavoidable. I doubt that it matters to George.

and the
>prop delay through the buffers isn't exactly precise...

How do you know that? I didn't specify the parts, other than max PD. They could
be implemented as a tapped delay line, passive or silicon. Or one could trim Vcc
to tweak prop delay. There are lots of possibilities.

Post something better.

John Fields

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Mar 7, 2013, 5:36:35 PM3/7/13

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On Thu, 07 Mar 2013 13:32:22 -0800, John Larkin

---
Maybe not, but I posted a message to him asking for clarification,
just to resolve the issue.

You, on the other hand, opted to second-guess him and subjugate him to
your will.
---

> and the prop delay through the buffers isn't exactly precise...
>
>How do you know that?

---
I read the data sheet.
---

>I didn't specify the parts, other than max PD.

---
Not true; you specified the HC14
---

>They could be implemented as a tapped delay line, passive or silicon. Or one could trim >Vcc to tweak prop delay. There are lots of possibilities.

---
Which you didn't allude to in your initial response, so now they're
afterthoughts which you're trying to use to dig yourself out of the
grave you dug for yourself.
---

>Post something better.

---
OK,

From "Einstein's Theory of Relativity" by Max Born, we have:
v²
sqrt (1-beta²) = sqrt 1- ---
ac²

--
JF

John Larkin

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Mar 7, 2013, 5:48:53 PM3/7/13

to

On Thu, 07 Mar 2013 16:36:35 -0600, John Fields <jfi...@austininstruments.com>

What a sad old dork.

John Fields

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Mar 7, 2013, 6:02:37 PM3/7/13

to

On Thu, 07 Mar 2013 14:48:53 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 07 Mar 2013 16:36:35 -0600, John Fields <jfi...@austininstruments.com>
>wrote:
>
>>On Thu, 07 Mar 2013 13:32:22 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>>>Post something better.
>>
>>---
>>OK,
>>
>>From "Einstein's Theory of Relativity" by Max Born, we have:
>> v²
>>sqrt (1-beta²) = sqrt 1- ---
>> ac²
>
>What a sad old dork.

---
Commentary, but nothing relevant...

--
JF

Jim Thompson

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Mar 7, 2013, 6:19:36 PM3/7/13

to

On Thu, 07 Mar 2013 17:02:37 -0600, John Fields

<jfi...@austininstruments.com> wrote:

>On Thu, 07 Mar 2013 14:48:53 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Thu, 07 Mar 2013 16:36:35 -0600, John Fields <jfi...@austininstruments.com>
>>wrote:
>>
>>>On Thu, 07 Mar 2013 13:32:22 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>>>Post something better.
>>>
>>>---
>>>OK,
>>>
>>>From "Einstein's Theory of Relativity" by Max Born, we have:
>>> v²
>>>sqrt (1-beta²) = sqrt 1- ---
>>> ac²
>>
>>What a sad old dork.
>
>---
>Commentary, but nothing relevant...

Another one of JL's non-working "designs". A quick check of 74HC
proves my supposition that a 5ns wide pulse goes nowhere... at least
reliably... something JL never worries about... but that's what you
get when you're pompously ignorant.

| E-mail Icon at http://www.analog-innovations.com | 1962 |

Jamie

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Mar 7, 2013, 6:42:20 PM3/7/13

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I think you're going to have a little problem with that inverter in
regards to the speed you are referring to.

Jamie

John Larkin

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Mar 7, 2013, 7:02:49 PM3/7/13

to

I didn't say it was a 74HC, much less an HC14. Note that the delay elements are
non-inverting.

Having no ideas of your own, you two old hens are naturally hostile to ideas.

Design an original pulse stretcher concept, if you can. Post it here.

This one makes pulses adjustable from 100 ps to 25 ns. How would you do that?

http://www.highlandtechnology.com/DSS/T240DS.shtml

bloggs.fred...@gmail.com

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Mar 7, 2013, 9:43:36 PM3/7/13

to

On Thursday, March 7, 2013 1:21:33 PM UTC-5, George Herold wrote:
> Hi guys, I need a little digital pulse stretcher. I've got pulses
>
> that are 5ns to 25ns in width, and I'd like to bump them all up to all
>
> be at least 10ns. I've got a few spare 74HC14 inverters. I was
>
> thinking of just feeding one through a diode followed by an R/C to
>
> ground. Any other ways? There might be an extra AND gate too.
>
> (not my circuit so I'm not quite sure.)
>

The 5ns is way out of line for HC. You can apply the pulse directly to an emitter follower loaded with parallel RC and then to HC to stretch it to any width you want. The BE junction is your diode. HC will not work reliably across VCC and temperature with anything less than about 25ns.

George Herold

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Mar 7, 2013, 10:35:33 PM3/7/13

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On Mar 7, 3:43 pm, John Fields <jfie...@austininstruments.com> wrote:
> On Thu, 7 Mar 2013 10:21:33 -0800 (PST), George Herold
>

Yeah there's already ~20ns of latency between the input pulse and the
output so a bit extra ain't too bad. I'll knock the 10pF down to 4.7

George H.

George Herold

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Mar 7, 2013, 10:36:48 PM3/7/13

to

On Mar 7, 3:56 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 7 Mar 2013 11:01:25 -0800 (PST), George Herold <gher...@teachspin.com>

> John Larkin Highland Technology Incwww.highlandtechnology.com jlarkin at highlandtechnology dot com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom timing and laser controllers
> Photonics and fiberoptic TTL data links
> VME analog, thermocouple, LVDT, synchro, tachometer

> Multichannel arbitrary waveform generators- Hide quoted text -
>
> - Show quoted text -

Whee... fun!

George H.

George Herold

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Mar 7, 2013, 10:45:44 PM3/7/13

to

On Mar 7, 4:08 pm, John Fields <jfie...@austininstruments.com> wrote:
> On Thu, 07 Mar 2013 12:56:22 -0800, John Larkin
>
>
>
>
>

> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >On Thu, 7 Mar 2013 11:01:25 -0800 (PST), George Herold <gher...@teachspin.com>

> JF- Hide quoted text -

>
> - Show quoted text -

Yeah in this case there's certainly already some delay. But it
doesn't really matter.
OK it matters.. it all adds to the built in latency of the device.
But at the moment there's some 'software' latency that's ~x10's as
bad.
So I can burn 10's of nanoseconds with abandon.

George H.

Vladimir Vassilevsky

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Mar 7, 2013, 10:48:14 PM3/7/13

to

On 3/7/2013 8:43 PM, bloggs.fred...@gmail.com wrote:
> On Thursday, March 7, 2013 1:21:33 PM UTC-5, George Herold wrote:
>> Hi guys, I need a little digital pulse stretcher. I've got
>> pulses
>>
>> that are 5ns to 25ns in width, and I'd like to bump them all up to
>> all
>>
>> be at least 10ns. I've got a few spare 74HC14 inverters. I was
>>
>> thinking of just feeding one through a diode followed by an R/C to
>>
>> ground. Any other ways? There might be an extra AND gate too.
>>
>> (not my circuit so I'm not quite sure.)
>>
>
> The 5ns is way out of line for HC.

The 5...6 ns per gate is what you can practically expect from today's HC.

VLV

George Herold

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Mar 7, 2013, 10:52:00 PM3/7/13

to

On Mar 7, 4:32 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 07 Mar 2013 15:08:49 -0600, John Fields <jfie...@austininstruments.com>

> wrote:
>
>
>
>
>
> >On Thu, 07 Mar 2013 12:56:22 -0800, John Larkin

> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >>On Thu, 7 Mar 2013 11:01:25 -0800 (PST), George Herold <gher...@teachspin.com>

> John Larkin Highland Technology Incwww.highlandtechnology.com jlarkin at highlandtechnology dot com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom timing and laser controllers
> Photonics and fiberoptic TTL data links
> VME analog, thermocouple, LVDT, synchro, tachometer

> Multichannel arbitrary waveform generators- Hide quoted text -

>
> - Show quoted text -

In this case I'm timing a pulse stream. But absolute time doesn't
matter as much as relative time. So as long as the prop. delay
doesn't stop more than one pulse from traveling down the signal chain,
then it may not matter.

George H.

bloggs.fred...@gmail.com

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Mar 7, 2013, 10:54:04 PM3/7/13

to

Please link to a datasheet- all I'm seeing is 20ns nominal performance on both Tpd's and minimum pulse widths into edge activated inputs like clk's, R's, and S's.

George Herold

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Mar 7, 2013, 10:56:53 PM3/7/13

to

On Mar 7, 6:19 pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-

Web-Site.com> wrote:
> On Thu, 07 Mar 2013 17:02:37 -0600, John Fields
>
>
>
>
>
> <jfie...@austininstruments.com> wrote:
> >On Thu, 07 Mar 2013 14:48:53 -0800, John Larkin

> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >>On Thu, 07 Mar 2013 16:36:35 -0600, John Fields <jfie...@austininstruments.com>

> >>wrote:
>
> >>>On Thu, 07 Mar 2013 13:32:22 -0800, John Larkin
> >>><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >>>>Post something better.
>
> >>>---
> >>>OK,
>
> >>>From "Einstein's Theory of Relativity" by Max Born, we have:
> >>> v²
> >>>sqrt (1-beta²) = sqrt 1- ---
> >>> ac²
>
> >>What a sad old dork.
>
> >---
> >Commentary, but nothing relevant...
>
> Another one of JL's non-working "designs". A quick check of 74HC
> proves my supposition that a 5ns wide pulse goes nowhere... at least
> reliably... something JL never worries about... but that's what you
> get when you're pompously ignorant.
>
> ...Jim Thompson
> --
> | James E.Thompson | mens |
> | Analog Innovations | et |
> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
> | Phoenix, Arizona 85048 Skype: Contacts Only | |
> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat |

> | E-mail Icon athttp://www.analog-innovations.com| 1962 |
>
> I love to cook with wine. Sometimes I even put it in the food.- Hide quoted text -

>
> - Show quoted text -

Yeah Jim the 5ns pulses weren't getting counted....
Sorry I missed a reply to you. There's a comparator on the input and
I put the diode R/C thing between it and the first 74HC14 gate...

George H.

George Herold

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Mar 7, 2013, 11:00:39 PM3/7/13

to

Cool 25 ns is just what I'd expect if I cut my C to 4.7pF

Thanks Fred.

George H.

Vladimir Vassilevsky

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Mar 7, 2013, 11:14:01 PM3/7/13

to

On 3/7/2013 9:54 PM, bloggs.fred...@gmail.com wrote:
> On Thursday, March 7, 2013 10:48:14 PM UTC-5, Vladimir Vassilevsky
> wrote:
>> On 3/7/2013 8:43 PM, bloggs.fred...@gmail.com wrote:
>>
>>> On Thursday, March 7, 2013 1:21:33 PM UTC-5, George Herold
>>> wrote:
>>
>>>> Hi guys, I need a little digital pulse stretcher. I've got
>>
>>>> pulses
>>
>>>>
>>
>>>> that are 5ns to 25ns in width, and I'd like to bump them all up
>>>> to
>>
>>>> all
>>
>>>>
>>
>>>> be at least 10ns. I've got a few spare 74HC14 inverters. I
>>>> was
>>
>>>>
>>
>>>> thinking of just feeding one through a diode followed by an R/C
>>>> to
>>
>>>>
>>
>>>> ground. Any other ways? There might be an extra AND gate
>>>> too.
>>
>>>>
>>
>>>> (not my circuit so I'm not quite sure.)
>>
>>>>
>>
>>>
>>
>>> The 5ns is way out of line for HC.
>>
>>
>>
>> The 5...6 ns per gate is what you can practically expect from
>> today's HC.
>>

> Please link to a datasheet- all I'm seeing is 20ns nominal
> performance on both Tpd's and minimum pulse widths into edge
> activated inputs like clk's, R's, and S's.

Didn't Karl Marx teach you communists that practice is criterion of
truth? Take a good scope, pulse generator and see for yourself.

VLV

bloggs.fred...@gmail.com

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Mar 8, 2013, 12:44:53 AM3/8/13

to

On Thursday, March 7, 2013 11:14:01 PM UTC-5, Vladimir Vassilevsky wrote:

> truth? Take a good scope, pulse generator and see for yourself.

Okay, you know what you measured, but you need to be real careful with layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capacitive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.

John Fields

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Mar 8, 2013, 2:18:53 AM3/8/13

to

On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>http://www.highlandtechnology.com/DSS/T240DS.shtml

---
That's not a pulse stretcher, cheater, that's a pulse _generator_.
--
JF

dagmarg...@yahoo.com

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Mar 8, 2013, 8:44:57 AM3/8/13

to

On Mar 8, 2:18 am, John Fields <jfie...@austininstruments.com> wrote:
> On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
>

> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >http://www.highlandtechnology.com/DSS/T240DS.shtml
>
> ---
> That's not a pulse stretcher, cheater, that's a pulse _generator_.
> --
> JF

A *triggered* pulse generator.

--
Cheers,
James Arthur

George Herold

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Mar 8, 2013, 8:45:37 AM3/8/13

to

Hi Fred, As Vlad said the HC series was really doing just fine with
10ns pulses and perhaps only 'missing' 1% of the 5 or 6 ns ones. I
don't have a commercial pulser that will do anything less than ~20ns,
so it's hard to test. I had a pulse swallower circuit on a piece of
copper clad, but I might have ripped it up to make something else...
Anyway I don’t see any reason not to play it safe and make the minimum
pulse 25ns.

My ‘scope is only 200MHz, so I’m not really sure I even believe the
5ns... what’s that rule of thumb for ‘scope bandwidth/ rise time? tau=
1/(3*BW) ?

George H.

John Larkin

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Mar 8, 2013, 9:54:50 AM3/8/13

to

On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfi...@austininstruments.com>
wrote:

It's a one-shot. It has no internal trigger. It generates no pulses.

And neither you nor Jim have a clue as to how this might be done.

We have a customer who wants us to take this down to 10 ps pulses. At that
point, I'm not sure that I know how that might be done. We're thinking about it.

Frank Miles

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Mar 8, 2013, 11:47:58 AM3/8/13

to

On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote:

> My ‘scope is only 200MHz, so I’m not really sure I even believe the
> 5ns... what’s that rule of thumb for ‘scope bandwidth/ rise time? tau=
> 1/(3*BW) ?

Very close. Tek always gave the formula: 0.35/BW ; it's based on the
semi-mythical gaussian bandpass characteristic. If aberrations are
significant, neither can be trusted.

You probably know the formula for estimating risetime when the
measurement approaches the instrument limits:
tr= sqrt(tmeas^2 - tinstr^2)
which of course only works when you already know that the pulses are
clean - which you probably can't tell with that scope.

John Fields

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Mar 8, 2013, 12:08:42 PM3/8/13

to

On Fri, 08 Mar 2013 06:54:50 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfi...@austininstruments.com>
>wrote:
>
>>On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>http://www.highlandtechnology.com/DSS/T240DS.shtml
>>
>>---
>>That's not a pulse stretcher, cheater, that's a pulse _generator_.
>
>It's a one-shot. It has no internal trigger. It generates no pulses.

---
Geez, and here I always thought that one-shots generated waveforms
with more-or-less crispy edges with a more-or less constant voltage
level between them.

You know, what we here in the real world call a "pulse".

Take a look at the first bulleted item on your data sheet and you'll
see that you do too, you fucking loon...

--
JF

John Fields

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Mar 8, 2013, 12:12:11 PM3/8/13

to

On Fri, 8 Mar 2013 05:44:57 -0800 (PST), dagmarg...@yahoo.com
wrote:

---
Yup; a "single-channel externally-triggered complementary-output pulse
generator", from Larkin's blurb.

--
JF

bloggs.fred...@gmail.com

unread,

Mar 8, 2013, 12:27:26 PM3/8/13

to

On Friday, March 8, 2013 8:45:37 AM UTC-5, George Herold wrote:

>
>
> My ‘scope is only 200MHz, so I’m not really sure I even believe the
>
> 5ns... what’s that rule of thumb for ‘scope bandwidth/ rise time? tau=
>
> 1/(3*BW) ?
>

Yes, assuming the probe is not a limitation. But the observed risetime is the RMS of signal + scope risetimes.
http://cp.literature.agilent.com/litweb/pdf/5988-8008EN.pdf

John Larkin

unread,

Mar 8, 2013, 12:46:41 PM3/8/13

to

On Fri, 08 Mar 2013 11:08:42 -0600, John Fields

<jfi...@austininstruments.com> wrote:

>On Fri, 08 Mar 2013 06:54:50 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfi...@austininstruments.com>
>>wrote:
>>
>>>On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>http://www.highlandtechnology.com/DSS/T240DS.shtml
>>>
>>>---
>>>That's not a pulse stretcher, cheater, that's a pulse _generator_.
>>
>>It's a one-shot. It has no internal trigger. It generates no pulses.
>
>---
>Geez, and here I always thought that one-shots generated waveforms
>with more-or-less crispy edges with a more-or less constant voltage
>level between them.
>
>You know, what we here in the real world call a "pulse".
>
>Take a look at the first bulleted item on your data sheet and you'll
>see that you do too, you fucking loon...

More uninformed whining. All you want to do is argue about words,
because you can't design electronics.

You don't like any of my pulse stretchers, so design a better one.
Post it here. Your great love Jim can do the same.

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

VME thermocouple, LVDT, synchro acquisition and simulation

George Herold

unread,

Mar 8, 2013, 12:52:29 PM3/8/13

to

On Mar 8, 11:47 am, Frank Miles <f...@u.washington.edu> wrote:
> On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote:
> > My ‘scope is only 200MHz, so I’m not really sure I even believe the
> > 5ns... what’s that rule of thumb for ‘scope bandwidth/ rise time? tau=
> > 1/(3*BW) ?
>
> Very close. Tek always gave the formula: 0.35/BW ; it's based on the
> semi-mythical gaussian bandpass characteristic. If aberrations are
> significant, neither can be trusted.
>
> You probably know the formula for estimating risetime when the
> measurement approaches the instrument limits:

> tr= sqrt(tmeas^2 - tinstr^2)

No I didn't know that. Thanks, I guess mostly I like to have minimal
instrumental effects :^)

George H.

John Larkin

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Mar 8, 2013, 1:07:46 PM3/8/13

to

On Fri, 8 Mar 2013 16:47:58 +0000 (UTC), Frank Miles
<f...@u.washington.edu> wrote:

>On Fri, 08 Mar 2013 05:45:37 -0800, George Herold wrote:
>
>> My ‘scope is only 200MHz, so I’m not really sure I even believe the
>> 5ns... what’s that rule of thumb for ‘scope bandwidth/ rise time? tau=
>> 1/(3*BW) ?
>
>Very close. Tek always gave the formula: 0.35/BW ; it's based on the
>semi-mythical gaussian bandpass characteristic. If aberrations are
>significant, neither can be trusted.

That used to be true. The high-end digital scopes that I've tested
lately don't seem to have gaussian response; they seem to be tweaked
for bandwidth bragging rights, and subsequently ring.

My "200 MHz" Tek DPO2024 rings a bit and has a rise time of 1.85 ns.

Vladimir Vassilevsky

unread,

Mar 8, 2013, 3:55:50 PM3/8/13

to

On 3/7/2013 2:36 PM, George Herold wrote:
> On Mar 7, 3:12 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:

>> On 3/7/2013 12:21 PM, George Herold wrote:
>>
>>> Hi guys, I need a little digital pulse stretcher. I've got pulses
>>> that are 5ns to 25ns in width, and I'd like to bump them all up to all
>>> be at least 10ns. I've got a few spare 74HC14 inverters. I was
>>> thinking of just feeding one through a diode followed by an R/C to
>>> ground. Any other ways? There might be an extra AND gate too.
>>> (not my circuit so I'm not quite sure.)
>>

>> Something like this:
>>
>> http://www.abvolt.com/misc/pulse_stretch.jpg
>>
>> You got the idea.
>>
> Yeah I was thinking of something like that too. The diode thing was
> an easy 'hack' and seems to be working just fine. (I stuck in 10k
> and 10pF and have about a 50ns minimum pulse.) Life is good.

Fie. Analog parts on the digital board.

http://www.abvolt.com/misc/pulse_stretch_2.jpg

This should satisfy most captious critics.

VLV

Phil Hobbs

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Mar 8, 2013, 3:59:36 PM3/8/13

to

It's actually more general than that--there's a Fourier transform
theorem that variances add under convolution, so providing the pulse
widths and rise times are defined in terms of the second moments, and
there are no loading effects due to cascading the two devices, this
formula works exactly.

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 USA
+1 845 480 2058

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

John Fields

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Mar 8, 2013, 4:08:02 PM3/8/13

to

On Fri, 08 Mar 2013 09:46:41 -0800, John Larkin
<jla...@highlandtechnology.com> wrote:

>On Fri, 08 Mar 2013 11:08:42 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Fri, 08 Mar 2013 06:54:50 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfi...@austininstruments.com>
>>>wrote:
>>>
>>>>On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
>>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>
>>>>>http://www.highlandtechnology.com/DSS/T240DS.shtml
>>>>
>>>>---
>>>>That's not a pulse stretcher, cheater, that's a pulse _generator_.
>>>
>>>It's a one-shot. It has no internal trigger. It generates no pulses.
>>
>>---
>>Geez, and here I always thought that one-shots generated waveforms
>>with more-or-less crispy edges with a more-or less constant voltage
>>level between them.
>>
>>You know, what we here in the real world call a "pulse".
>>
>>Take a look at the first bulleted item on your data sheet and you'll
>>see that you do too, you fucking loon...
>
>More uninformed whining.

---
Hey, you're the one with a data sheet touting your widget as a pulse
generator, and I'm agreeing with it, so what's your problem?
---

>All you want to do is argue about words, because you can't design electronics.

---
All you want to do is argue, about anything, in the vain hope that
some miracle will come around when you've made a mistake - and it's
been pointed out to you - and bail you out of the ocean of shit you
get yourself into with that silly macho facade of infallibility.

As for the "design" part, we've both seen my posting history, so we
both know you're just having a hissie fit.
---

>You don't like any of my pulse stretchers, so design a better one.

---
In your own words, they're not pulse stretchers, they're:

"single-channel externally-triggered complementary-output pulse
generator"(s).

and, having had no experience with them, I neither like them nor
dislike them.

I would like to see some more data, though; Zout, maximum trigger
rate, stuff like that...
---

>Post it here.

---
Sorry Charlie; too much work for too little return.

Especially when all you're looking for is something - anything - you
can mouth off against and start another harangue to keep you in the
limelight.
---

>Your great love Jim can do the same.

---
Over the years, after a rocky beginning, I've come to appreciate Jim
as a friend, a colleague, and a very clever circuit designer, and what
love I have for him is fraternal.

I don't think Jim will take your bait, but you invoke the malevolent
accusation-of-homosexuality-with-no-basis-in-fact theme again? Seems
like a flag you wave _way_ more often than necessary, Senator
McCarthy.

Early on, when you first started posting here, I felt some affection
for you, but as time passed and your agenda crystallized it became
apparent that your aim was nothing more than self-aggrandizement.

I now feel nothing but contempt for you.

--
JF

Spehro Pefhany

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Mar 8, 2013, 9:38:55 AM3/8/13

to

On Fri, 8 Mar 2013 05:45:37 -0800 (PST), George Herold
<ghe...@teachspin.com> wrote:

>On Mar 8, 12:44�am, bloggs.fredbloggs.f...@gmail.com wrote:
>> On Thursday, March 7, 2013 11:14:01 PM UTC-5, Vladimir Vassilevsky wrote:
>> > truth? Take a good scope, pulse generator and see for yourself.
>>
>> Okay, you know what you measured, but you need to be real careful with layout using that parts family. It used to be a point of advantage for a logic family that it was unresponsive to full logic level transitions of duration less than the fastest edge rates in the system. Interwiring capacitive coupling into a nice high impedance input converts the transition into a nice square pulse there. I think Lenin covered that one.
>
>Hi Fred, As Vlad said the HC series was really doing just fine with
>10ns pulses and perhaps only 'missing' 1% of the 5 or 6 ns ones. I

The tinylogic one-shot that John mentioned is guaranteed to trigger
off 2.5ns pulses (with a 5V 'Vcc'). Available in a nice friendly
0.65mm pitch 8-pin package (also a 0.5mm pitch or 1 x 2mm BGA if you
are in need of pain).

John Larkin

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Mar 8, 2013, 4:24:35 PM3/8/13

to

On Fri, 08 Mar 2013 15:08:02 -0600, John Fields

Well, the feeling doesn't seem to be mutual; he's dissing you lately.
I suppose his goal is to be universally disliked.

John Larkin

unread,

Mar 8, 2013, 4:27:50 PM3/8/13

to

On Fri, 08 Mar 2013 14:55:50 -0600, Vladimir Vassilevsky

The low input flushes the delay chain. Cute.

John Fields

unread,

Mar 8, 2013, 4:56:16 PM3/8/13

to

On Fri, 08 Mar 2013 13:24:35 -0800, John Larkin

---
You think?

My take on it is that he's criticizing me for interacting with
assholes like you who very rarely have anything good to say and am,
therefore, wasting bandwidth.

He's right, kinda,

But you still need your comeuppance.
---

>I suppose his goal is to be universally disliked.

---
Well, since you're not the universe and he has clients who fall
outside of your sphere of influence, I suspect your wish for him to be
universally disliked won't be fulfilled.

More to the point, however, why would you want him to be universally
disliked?

--
JF

dagmarg...@yahoo.com

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Mar 8, 2013, 8:26:12 PM3/8/13

to

That's pretty, but if the part's fast it might not meet George's min.
output pulse needs. An R-C or two would fix that.

<ducks>

--
Cheers,
James Arthur

George Herold

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Mar 8, 2013, 8:31:47 PM3/8/13

to

On Mar 8, 9:38 am, Spehro Pefhany <speffS...@interlogDOTyou.knowwhat>
wrote:

> On Fri, 8 Mar 2013 05:45:37 -0800 (PST), George Herold
>

Sweet, I think a nice one shot is the right medicine.
It looks like I'll stretch it out to ~200ns, not a big deal
with 1us bins, the first time bin is ~20% 'short'.
We'll document it in the manual and specs,
70% of our users will never notice.

Hey, we should use the 200ns pulse as the monitor output!
maybe they'll notice if it's on the 'scope.

I'm not sure why I didn't have a one-shot in to begin with.
(there's been some 'vibe' that one shots are bad.(?)
It all seems so obvious in retrospect.

George H.

Jim Thompson

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Mar 8, 2013, 9:00:33 PM3/8/13

to

On Fri, 8 Mar 2013 17:26:12 -0800 (PST), dagmarg...@yahoo.com
wrote:

It's so crappy, it's almost Larkinesque. The f...ing "specification"
was to widen a 5ns sliver. A 5ns sliver won't even produce a sigh out
of 74HC stuff.

| E-mail Icon at http://www.analog-innovations.com | 1962 |

John Larkin

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Mar 8, 2013, 9:13:18 PM3/8/13

to

On Fri, 08 Mar 2013 15:56:16 -0600, John Fields <jfi...@austininstruments.com>

Design something. That's how things are counted here.

--

John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

John Larkin

unread,

Mar 8, 2013, 9:14:45 PM3/8/13

to

So design something. Do you remember how?

Jamie

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Mar 8, 2013, 9:31:34 PM3/8/13

to

:)

Jamie

Bill Sloman

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Mar 8, 2013, 9:48:47 PM3/8/13

to

On Mar 9, 3:54 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfie...@austininstruments.com>

> wrote:
>
> >On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >>http://www.highlandtechnology.com/DSS/T240DS.shtml
>
> >---
> >That's not a pulse stretcher, cheater, that's a pulse _generator_.
>
> It's a one-shot. It has no internal trigger. It generates no pulses.
>
> And neither you nor Jim have a clue as to how this might be done.
>
> We have a customer who wants us to take this down to 10 ps pulses. At that
> point, I'm not sure that I know how that might be done. We're thinking about it.

http://books.google.co.nz/books?id=-pi4vP6xMOQC&pg=PA571&lpg=PA571&dq=%22emitter-coupled%22+monostable&source=bl&ots=CFsGlVE2YN&sig=TUbjQhyQPk_cd5tj_UKlIhFVXt8&hl=en&sa=X&ei=TZw6UYmmPMeNyAHA4oHYAg&ved=0CEIQ6AEwAw#v=onepage&q=%22emitter-coupled%22%20monostable&f=false

describes the emitter-coupled monostable. Put one together out of a
pair of wide-band tansistors - BFR92 or better - with 33R up against
each base, and you can cetainly get below 10nsec. Since the mechanism
depends on the change of base-emitter impedance with emitter current,
it isn't as easy as it might be to get a wide range of output pulse
widths.

Jim Thompson could probably remember a better solution for you. The
long-obsolete MC10198 ECL monostable

http://www.digchip.com/datasheets/parts/datasheet/343/MC10198-pdf.php

could just get down to 10nsec, but we used two of them when we wanted
to offer long pulses as well - being able to switch in bigger
capacitors put too much stray capacitance on the relevant input pin
for 10nsec operation.

Something boringly obvious with a constant current ramp and a fast
comparator would do the job, but - as with the MC10198, being able to
switch in bigger capacitors to generate much longer pulses is probably
incompatible with a 10nsec pulse width.

--
Bill Sloman, Sydney

John Larkin

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Mar 8, 2013, 11:18:42 PM3/8/13

to

On Fri, 8 Mar 2013 18:48:47 -0800 (PST), Bill Sloman <bill....@ieee.org>
wrote:

I want 10 picoseconds, not 10 ns. I already sell boxes that go down to 100 ps
pulse width.

http://www.highlandtechnology.com/DSS/T240DS.shtml

I just need another factor of 10.

Bill Sloman

unread,

Mar 9, 2013, 5:13:57 AM3/9/13

to

On Mar 9, 5:18 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Fri, 8 Mar 2013 18:48:47 -0800 (PST),BillSloman<bill.slo...@ieee.org>

> wrote:
>
>
>
>
>
>
>
>
>
> >On Mar 9, 3:54 am, John Larkin
> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> On Fri, 08 Mar 2013 01:18:53 -0600, John Fields <jfie...@austininstruments.com>
> >> wrote:
>
> >> >On Thu, 07 Mar 2013 16:02:49 -0800, John Larkin
> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >> >>http://www.highlandtechnology.com/DSS/T240DS.shtml
>
> >> >---
> >> >That's not a pulse stretcher, cheater, that's a pulse _generator_.
>
> >> It's a one-shot. It has no internal trigger. It generates no pulses.
>
> >> And neither you nor Jim have a clue as to how this might be done.
>
> >> We have a customer who wants us to take this down to 10 ps pulses. At that
> >> point, I'm not sure that I know how that might be done. We're thinking about it.
>

> >http://books.google.co.nz/books?id=-pi4vP6xMOQC&pg=PA571&lpg=PA571&dq...

>
> >describes the emitter-coupled monostable. Put one together out of a
> >pair of wide-band tansistors - BFR92 or better - with 33R up against
> >each base, and you can cetainly get below 10nsec. Since the mechanism
> >depends on the change of base-emitter impedance with emitter current,
> >it isn't as easy as it might be to get a wide range of output pulse
> >widths.
>
> >Jim Thompson could probably remember a better solution for you. The
> >long-obsolete MC10198 ECL monostable
>
> >http://www.digchip.com/datasheets/parts/datasheet/343/MC10198-pdf.php
>
> >could just get down to 10nsec, but we used two of them when we wanted
> >to offer long pulses as well - being able to switch in bigger
> >capacitors put too much stray capacitance on the relevant input pin
> >for 10nsec operation.
>
> >Something boringly obvious with a constant current ramp and a fast
> >comparator would do the job, but - as with the MC10198, being able to
> >switch in bigger capacitors to generate much longer pulses is probably
> >incompatible with a 10nsec pulse width.
>
> I want 10 picoseconds, not 10 ns. I already sell boxes that go down to 100 ps
> pulse width.
>
> http://www.highlandtechnology.com/DSS/T240DS.shtml
>
> I just need another factor of 10.

Interesting. If electromagnetic radiation propagates 20cm in 1nsec in
ordinary dielectrics, 10psec is 2mm, and it's going to be a bit tricky
to provide connections that don't introduce significant impedance
discontinuities. Are you planning on designing stuff that surface
mounts onto his printed circuit?

Since microstrip is intrinsicly dispersive, strip line might be
better, and he'd have to sandwich your contribution.

Clearly a fresh field to conquer, not exactly nano-engineering, but
definitely one for the tiny-minded.

--
Bill Sloman, Sydney

John Fields

unread,

Mar 9, 2013, 8:01:18 AM3/9/13

to

On Fri, 08 Mar 2013 18:13:18 -0800, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>Design something. That's how things are counted here.

---
Fuck you.

I've posted enough stuff over the last fifteen years or so to have
established my reputation as a designer, and I certainly don't have to
dance to your tune to prove anything to anyone.

--
JF

Jim Thompson

unread,

Mar 9, 2013, 10:17:23 AM3/9/13

to

Well? Larkin has certainly posted A LOT MORE... no matter that it's
just non-functional crap >:-}

John Fields

unread,

Mar 9, 2013, 10:44:43 AM3/9/13

to

On Sat, 09 Mar 2013 08:17:23 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Sat, 09 Mar 2013 07:01:18 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Fri, 08 Mar 2013 18:13:18 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>Design something. That's how things are counted here.
>>
>>---
>>Fuck you.
>>
>>I've posted enough stuff over the last fifteen years or so to have
>>established my reputation as a designer, and I certainly don't have to
>>dance to your tune to prove anything to anyone.
>
>Well? Larkin has certainly posted A LOT MORE... no matter that it's
>just non-functional crap >:-}
>
> ...Jim Thompson

---
I think Larkin is far and away the most copious poster here of
off-topic material.

--
JF

Jim Thompson

unread,

Mar 9, 2013, 10:58:05 AM3/9/13

to

On Sat, 09 Mar 2013 09:44:43 -0600, John Fields

<jfi...@austininstruments.com> wrote:

>On Sat, 09 Mar 2013 08:17:23 -0700, Jim Thompson
><To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
>>On Sat, 09 Mar 2013 07:01:18 -0600, John Fields
>><jfi...@austininstruments.com> wrote:
>>
>>>On Fri, 08 Mar 2013 18:13:18 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>Design something. That's how things are counted here.
>>>
>>>---
>>>Fuck you.
>>>
>>>I've posted enough stuff over the last fifteen years or so to have
>>>established my reputation as a designer, and I certainly don't have to
>>>dance to your tune to prove anything to anyone.
>>
>>Well? Larkin has certainly posted A LOT MORE... no matter that it's
>>just non-functional crap >:-}
>>
>> ...Jim Thompson
>---
>I think Larkin is far and away the most copious poster here of
>off-topic material.

Yep. Mostly narcissistic nonsense. He must forever be on stage to
satisfy that BU-grade narcissism >:-}

John Larkin

unread,

Mar 9, 2013, 11:13:14 AM3/9/13

to

On Sat, 09 Mar 2013 07:01:18 -0600, John Fields <jfi...@austininstruments.com>
wrote:

>On Fri, 08 Mar 2013 18:13:18 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>Design something. That's how things are counted here.
>
>---
>Fuck you.
>
>I've posted enough stuff over the last fifteen years or so to have
>established my reputation as a designer,

Buggy hairballs, usually.

John Larkin

unread,

Mar 9, 2013, 11:15:44 AM3/9/13

to

On Sat, 9 Mar 2013 02:13:57 -0800 (PST), Bill Sloman <bill....@ieee.org>
wrote:

Naturally.

Are you planning on designing stuff that surface
>mounts onto his printed circuit?

No, onto mine. My output would be a coax connector.

>
>Since microstrip is intrinsicly dispersive, strip line might be
>better, and he'd have to sandwich your contribution.
>
>Clearly a fresh field to conquer, not exactly nano-engineering, but
>definitely one for the tiny-minded.

You say that like it's a bad thing.

John Fields

unread,

Mar 9, 2013, 12:26:20 PM3/9/13

to

On Sat, 09 Mar 2013 08:13:14 -0800, John Larkin

<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 09 Mar 2013 07:01:18 -0600, John Fields <jfi...@austininstruments.com>
>wrote:
>
>>On Fri, 08 Mar 2013 18:13:18 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>Design something. That's how things are counted here.
>>
>>---
>>Fuck you.
>>
>>I've posted enough stuff over the last fifteen years or so to have
>>established my reputation as a designer,
>
>Buggy hairballs, usually.

---
http://en.wikipedia.org/wiki/Proof_by_assertion

--
JF

Message has been deleted

Bill Sloman

unread,

Mar 9, 2013, 4:32:18 PM3/9/13

to

On Mar 10, 5:15 am, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Sat, 9 Mar 2013 02:13:57 -0800 (PST),BillSloman<bill.slo...@ieee.org>

Do you have a specific connector in mind? SMA crapped out at 18GHz.
Somebody has obviously introduced something better since then, but
Farnell wasn't stocking whatever it is when I last looked,

> >Since microstrip is intrinsicly dispersive, strip line might be
> >better, and he'd have to sandwich your contribution.
>
> >Clearly a fresh field to conquer, not exactly nano-engineering, but
> >definitely one for the tiny-minded.
>
> You say that like it's a bad thing.

It's true that there is a deliberate ambiguity there.

--
Bill Sloman, Sydney

Bill Sloman

unread,

Mar 9, 2013, 4:49:06 PM3/9/13

to

On Mar 10, 4:44 am, John Fields <jfie...@austininstruments.com> wrote:
> On Sat, 09 Mar 2013 08:17:23 -0700, Jim Thompson
>
>
>
>
>
>
>
>
>
> <To-Email-Use-The-Envelope-I...@On-My-Web-Site.com> wrote:
> >On Sat, 09 Mar 2013 07:01:18 -0600, John Fields
> ><jfie...@austininstruments.com> wrote:
>
> >>On Fri, 08 Mar 2013 18:13:18 -0800, John Larkin
> >><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>
> >>>Design something. That's how things are counted here.
>
> >>---
> >>Fuck you.
>
> >>I've posted enough stuff over the last fifteen years or so to have
> >>established my reputation as a designer, and I certainly don't have to
> >>dance to your tune to prove anything to anyone.
>
> >Well? Larkin has certainly posted A LOT MORE... no matter that it's
> >just non-functional crap >:-}

> ---
> I think Larkin is far and away the most copious poster here of
> off-topic material.

He's certainly the most copious poster here over the long term - 31024
posts. Eeyore is still second at about 19,000, I'm third with 18393
and Jim is fifth at 17611, just after Mike Terrell.

The Google statistics don't separate on-topic and off-topic posts. My
impreesion is that Jim Thompson posts a higher proportion of off-topic
stuff than John Larkin, but it isn't the kind of question for which
it's worth going to the trouble of finding an answer.

--
Bill Sloman, Sydney

John Fields

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Mar 9, 2013, 5:24:22 PM3/9/13

to

---
Your move back to Oz seems to have given you back some vigor; welcome
to the fray!

--
JF

John Larkin

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Mar 9, 2013, 5:50:25 PM3/9/13

to

On Sat, 9 Mar 2013 13:32:18 -0800 (PST), Bill Sloman <bill....@ieee.org>
wrote:

Whatever the load (a lithium niobate EOM) uses, I guess. 2.5 mm maybe, which is
SMA matable. I'd want PCB edge-launch. Launching into the connector is the scary
part.

>
>> >Since microstrip is intrinsicly dispersive, strip line might be
>> >better, and he'd have to sandwich your contribution.
>>
>> >Clearly a fresh field to conquer, not exactly nano-engineering, but
>> >definitely one for the tiny-minded.
>>
>> You say that like it's a bad thing.
>
>It's true that there is a deliberate ambiguity there.

If you get obnoxious again, I'll ignore you again. Your call.

John Larkin

unread,

Mar 9, 2013, 5:53:55 PM3/9/13

to

On Sat, 09 Mar 2013 12:23:18 -0800, Fred Abse <excret...@invalid.invalid>
wrote:

>On Fri, 08 Mar 2013 10:07:46 -0800, John Larkin wrote:
>
>> That used to be true. The high-end digital scopes that I've tested lately
>> don't seem to have gaussian response; they seem to be tweaked for
>> bandwidth bragging rights, and subsequently ring.
>>
>> My "200 MHz" Tek DPO2024 rings a bit and has a rise time of 1.85 ns.
>
>3dB bandwidth versus rise time used to be the test for 'scope spec
>"cheats". It's dead easy to make things look better than they really are.
>
>Tek service manuals used to be quite explicit about setting up Y
>amplifiers for minimum overshoot and ringing. Properly set up, the
>correlation between 3dB bandwith and rise time, using the 0.35 rule of
>thumb was quite close. Nearly every vertical amplifier I've come across,
>apart from the 50 ohm ones, has been overcompensated at the HF end.

Here it is:

https://dl.dropbox.com/u/53724080/Gear/DPO2024_rise.JPG

Frankly, Tektronix is cheating.

Jim Thompson

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Mar 9, 2013, 6:07:14 PM3/9/13

to

Indeed! Technical discussion without insult. I'll remove Sloman's
filter ;-)

As for Larkin... he only shows boxes, never a WORKING schematic, or
one that can be verified.

5ns to whatever is trivial on a custom CMOS chip... 10's of
picoseconds level of performance.

Now-a-days, 500MHz CMOS is passé.

Bill Sloman

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Mar 9, 2013, 6:13:25 PM3/9/13

to

One-shots are really chunks of analog electronics, and don't fit
perfectly into all-digital systems. Decoupling the 5V supply at the
monostable to the wrong 0V track can be a real problem.

If the track running from the monostable to the timing capacitance is
too long, or runs close up against an active trace, cross-talk can
make the output pulse lengths erratic. Analog designers tend to be
conscious of stuff like that. Digital designers tend to over-simplify
and find out the hard way.

--
Bill Sloman, Sydney

John Larkin

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Mar 9, 2013, 6:40:49 PM3/9/13

to

On Fri, 8 Mar 2013 17:31:47 -0800 (PST), George Herold <ghe...@teachspin.com>
wrote:

One-shots are politically incorrect, the legacy of days past when far too many
people designed asynchronous, hazardous, glitchy hairballs. Moto sold a DTL part
that was absurdly noise sensitive, and that contributed to the bad reputation.

They can be handy, used carefully.

bloggs.fred...@gmail.com

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Mar 9, 2013, 6:51:51 PM3/9/13

to

On Friday, March 8, 2013 3:59:36 PM UTC-5, Phil Hobbs wrote:

> It's actually more general than that--there's a Fourier transform
>
> theorem that variances add under convolution, ...

There is? It seems that is a result only for normal distributions.

>
> 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 USA
>
> +1 845 480 2058
>
>
>
> hobbs at electrooptical dot net
>
> http://electrooptical.net

George Herold

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Mar 9, 2013, 7:09:30 PM3/9/13

to

Yup, I'll do the schematic and look over the layout.
I was drawing on the white board and explaining the circuit to 'the
boss' and I drew a line between the comparator and first HC14, this
sides analog, that's digital, The diode RC thing is on the analog side
of the circuit, I'll put the one shot in the same place.

George H.

> If the track running from the monostable to the timing capacitance is
> too long, or runs close up against an active trace, cross-talk can
> make the output pulse lengths erratic. Analog designers tend to be
> conscious of stuff like that. Digital designers tend to over-simplify
> and find out the hard way.
>
> --

> Bill Sloman, Sydney- Hide quoted text -
>
> - Show quoted text -

George Herold

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Mar 9, 2013, 7:24:42 PM3/9/13

to

On Mar 9, 6:40 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Fri, 8 Mar 2013 17:31:47 -0800 (PST), George Herold <gher...@teachspin.com>

> John Larkin Highland Technology Incwww.highlandtechnology.com jlarkin at highlandtechnology dot com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom timing and laser controllers
> Photonics and fiberoptic TTL data links
> VME analog, thermocouple, LVDT, synchro, tachometer

> Multichannel arbitrary waveform generators- Hide quoted text -

>
> - Show quoted text -

The last time I used a one shot was back in '93. (real TTL)
Two of them set the pulse lengths in a NMR spectrometer.

George H.

Jim Thompson

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Mar 9, 2013, 7:37:11 PM3/9/13

to

I rarely use "one-shots", but I regularly use "stretchers" in my
custom chips... follows input up, then delayed drop-out.

Phil Hobbs

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Mar 9, 2013, 7:46:14 PM3/9/13

to

On 3/9/2013 6:51 PM, bloggs.fred...@gmail.com wrote:
> On Friday, March 8, 2013 3:59:36 PM UTC-5, Phil Hobbs wrote:
>
>> It's actually more general than that--there's a Fourier transform
>> theorem that variances add under convolution, ...
> There is? It seems that is a result only for normal distributions.

Yup. From the derivative theorem, the variance is proportional to the
second derivative of the transform, evaluated at zero frequency. To
within a constant factor that depends on your Fourier transform definition,

int(-inf to inf) [t**2 * h(t)]
var(h) = ------------------------------- = H''(0)/H(0)
int(-inf to inf) [h(t)]

Because the function is real, its transform is Hermitian, i.e. the real
part is even and the imaginary part is odd. Even-order derivatives of
an odd function vanish at the origin, as do odd-order derivatives of an
even function.

When you convolve g(t) and h(t), the transform is G(f)H(f). The
variance of this is proportional to the normalized second derivative at
the origin, as before. Ignoring a possible constant of proportionality
that we don't care about,

d(GH)/df = GH' + HG' so

d**2/df**2[GH]| H(0)G''(0) + G(0)H''(0) + 2G'H'
var(g*h) = --------------| = -------------------------------
GH |f=0 H(0)G(0)

G''(0) H''(0) 2G'(0)H'(0)
= ------- + -------- + ------------
G(0) H(0) H(0)G(0)

The first term is the variance of G, the second is the variance of H,
and the third is zero if either G or H is an even function.

There is a slightly more subtle condition that will make the third term
zero for any choice of g and h: that the first moment of either h(t) or
g(t) is zero, i.e. that at least one of them has its centroid at t=0,
which makes its first derivative zero at f=0.

It is always possible to satisfy this condition by an appropriate choice
of the time origin, so if you'll allow me to slide over that rather
trivial issue(*), variances add under convolution.

Cheers

Phil Hobbs

(*) The reason for this is the effect of a shift of origin on the
variance. If you convolve a function centred at t=5 with one centred at
t=3, the convolution's centroid is at t=8. If you're computing the
variance as the second moment about t=0, this will make a big
difference, but it doesn't change the shape of the resulting convolution
function. Forcing one of them to have its centroid at 0 gets rid of
this shift of time origin.

--

George Herold

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Mar 9, 2013, 8:05:03 PM3/9/13

to

On Mar 9, 7:46 pm, Phil Hobbs <pcdhSpamMeSensel...@electrooptical.net>
wrote:

Awesome... (Be careful what you ask for.)

Phil, If I mix two lasers together on a photodiode and look at the
bandwidth of the beat note to measure the laser bandwidth.. Is the
measured bandwidth the quadrature sum of the individual lasers (as
above for rise times, noise..) or does the power law nature of the PD
put a twist on it?

George H.

John Larkin

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Mar 9, 2013, 8:35:54 PM3/9/13

to

On Sat, 9 Mar 2013 16:24:42 -0800 (PST), George Herold <ghe...@teachspin.com>
wrote:

They are handy for winking LEDs. And there is my almost-famous double-tach/FM
discriminator circuit:

https://dl.dropbox.com/u/53724080/Circuits/DoubleTach.jpg

--

John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Phil Hobbs

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Mar 9, 2013, 9:06:39 PM3/9/13

to

> Awesome... (Be careful what you ask for.)
>
> Phil, If I mix two lasers together on a photodiode and look at the
> bandwidth of the beat note to measure the laser bandwidth.. Is the
> measured bandwidth the quadrature sum of the individual lasers (as
> above for rise times, noise..) or does the power law nature of the PD
> put a twist on it?
>

Hmm, no good deed goes unpunished. ;)

The PD is square law, but it isn't E**2, it's |E**2|, so to be
completely safe you have to stay in real-valued functions (sin and cos)
and not complex exponentials. (At least at first.)

Assuming that the relative phase of the two beams depends only on time,
i.e. that they're both really really single transverse mode, then
shining E1(x, y, t) and E2(x, y, t) on a sufficiently large photodiode
will get you

i_photo(t) = int(-inf < x < inf) int(-inf < y < inf)[ R|(E1(x,y,t) +
E2(x,y,t)|**2]dxdy

= R int int[ |E1|**2 + |E2|**2 + 2 Re{E1 E2*}]dxdy

where R is some constant (R is the responsivity if E**2 has units of
watts per square metre, but it doesn't matter here).

With a large enough beat frequency, we can regard E1**2 and E2**2 as DC
and filter them out. (Since the negative frequencies are twice as far
away as that, we can use the complex exponential notation with no
worries.) So at AC, all we get is

i_AC = 2R Re {int int[ E1(x,y,t)E2*(x,y,t)]dxdy }

If both lasers are single transverse mode, this integral is proportional
to Re{E1(0,0,t) E2*(0,0,t)}. Since the beat frequency is large, we
sample all relative phases of E1 and E2 much more rapidly than their
fluctuations, so we pretty much get an honest multiplication.
Multiplying them in the time domain is convolving them in the frequency
domain, so yes, the frequency variances add, *provided they're computed
around the nominal beat frequency*. Of course nobody in his right mind
would do anything else, but a computer might. ;)

The only thing that modifies this significantly is the frequency
response of the photodiode and the electrical measurement system.

Cheers

Phil Hobbs

Message has been deleted

John Larkin

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Mar 10, 2013, 2:44:29 PM3/10/13

to

On Sun, 10 Mar 2013 09:45:33 -0700, Fred Abse <excret...@invalid.invalid>
wrote:

>On Sat, 09 Mar 2013 14:53:55 -0800, John Larkin wrote:
>
>> Here it is:
>>
>> https://dl.dropbox.com/u/53724080/Gear/DPO2024_rise.JPG
>>
>> Frankly, Tektronix is cheating.
>

>Using the "0.35" rule, 1.865ns equates to 187.7MHz BW.
>
>Not far below 200MHz, which is 1.75ns.

Tek scopes used to give you gaussian response and a bit more than the specified
bandwidth, not less. It's like Budweiser watering down the beer.

>
>I can think of a few reasons:
>
>Were you using a hi-Z probe, or a 50 ohm (internal or external?)
>terminated measurement?

I connected an SD24 TDR head to the scope input through a short hardline. The SD
makes a roughly 20 ps, ultra-clean 50-ohm step.

>
>Interestingly, a 200MHz scope with a 500MHz probe, theoretically, would
>show 1.88ns risetime (186MHz BW).
>
>I've seen some commercial BNC through terminations start to get
>sticky around 200MHz, and be quite useless at 500MHz. An SMA terminator on
>a tee with adaptors outperforms quite dramatically.

I used a short SMA-SMA hardline and an SMA-BNC adapter. That should be good to
several GHz. BNCs are surprisingly good.

>
>If your scope provides 50 ohm inputs, I'd be inclined to TDR them.
>
>Another point; how does that scope measure risetime? Does it calculate the
>10% and 90% from the peak of the overshoot (wrong), or from the flat
>portion (correct)?

Don't know. It does overshoot enough to matter.

JW

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Mar 11, 2013, 7:31:11 AM3/11/13

to

On Sat, 9 Mar 2013 13:32:18 -0800 (PST) Bill Sloman <bill....@ieee.org>
wrote in Message id:
<e3ac026f-b80e-4710...@c6g2000yqh.googlegroups.com>:

>
>Do you have a specific connector in mind? SMA crapped out at 18GHz.
>Somebody has obviously introduced something better since then, but
>Farnell wasn't stocking whatever it is when I last looked,

SMP?

http://www.molex.com/molex/products/family?key=smp&channel=products&chanName=family&pageTitle=Introduction&parentKey=rf_microwave_coax_connectors

George Herold

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Mar 11, 2013, 10:00:43 AM3/11/13

to

On Mar 9, 10:06 pm, Phil Hobbs

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -

>
> - Show quoted text -

Cool, thanks Phil, (In practice I just quote the laser bandwidth as
the beat note bandwidth and ignore the above convolution.)
Ahh, what's the line about the PD size "on a sufficiently large
photodiode" refer too?
(I used this tiny EOT photodiode ET-2030.)

George H.

Phil Hobbs

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Mar 11, 2013, 10:03:34 AM3/11/13

to

1.8 mm usually.

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

Phil Hobbs

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Mar 11, 2013, 10:05:43 AM3/11/13

to

If the PD is too small, spatial fringes won't average out to zero, so
orthogonality doesn't quite work.

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

bloggs.fred...@gmail.com

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Mar 14, 2013, 11:49:59 PM3/14/13

to

Okay, thanks, don't think I've run into that kind of general analysis before. There is a more thorough rehash here:
Circuits, Signals, and Systems, Volume 2
By William McC. Siebert

Chap 16, but they omit the pages getting into the blasted second moments analysis:

http://books.google.com/books?id=zBTUiIrb2WIC&pg=PA42&dq=Circuits,+Signals,+and+Systems,+Volume+2++By+William+McC.+Siebert&hl=en&sa=X&ei=LphCUaanBbWo4AP5-YCoBA&ved=0CDgQ6AEwAA#v=onepage&q=Circuits%2C%20Signals%2C%20and%20Systems%2C%20Volume%202%20%20By%20William%20McC.%20Siebert&f=false

Phil Hobbs

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Mar 15, 2013, 2:50:03 AM3/15/13

to

> Okay, thanks, don't think I've run into that kind of general analysis before. There is a more thorough rehash here:
> Circuits, Signals, and Systems, Volume 2
> By William McC. Siebert
>
> Chap 16, but they omit the pages getting into the blasted second moments analysis:
>
> http://books.google.com/books?id=zBTUiIrb2WIC&pg=PA42&dq=Circuits,+Signals,+and+Systems,+Volume+2++By+William+McC.+Siebert&hl=en&sa=X&ei=LphCUaanBbWo4AP5-YCoBA&ved=0CDgQ6AEwAA#v=onepage&q=Circuits%2C%20Signals%2C%20and%20Systems%2C%20Volume%202%20%20By%20William%20McC.%20Siebert&f=false
>

Fourier and two-sided Laplace transforms are of course equivalent
(requiring only a trivial change of variables). I learned about
one-sided Laplace transforms in some undergrad math class, and promptly
ditched them because the inverse is such a mess. I don't think I've
ever used a one-sided transform in real life.

When I need to worry about the implicit step function due to causality
constraints or boundary conditions, I can put that in by hand at the
end, instead of carrying it along throughout the calculation, which is a
huge pain and completely unnecessary. (I do often use the s notation
instead of j 2 pi f, because it saves writing and reduces blunders.)

I'm a big fan of the Bracewell approach, probably partly because he was
such an engaging lecturer, but mostly because it's so useful and so easy
to remember once you get the hang of it.

http://www.amazon.com/The-Fourier-Transform-Its-Applications/dp/0073039381

Cheers

Phil Hobbs