On Mon, 12 Nov 2012 16:02:51 -0500, legg <l...@nospam.magma.ca> wrote:
>On Mon, 12 Nov 2012 12:41:46 -0700, Jim Thompson
><To-Email-Use-The-Envelope-I...@On-My-Web-Site.com> wrote:
>>On Mon, 12 Nov 2012 14:22:48 -0500, legg <l...@nospam.magma.ca> wrote:
>>>On Mon, 12 Nov 2012 09:55:50 +0100, o pere o <m...@somewhere.net> wrote:
><snip>
>>>>>>> The 2n2222a model may be missing (from inspection of popular models)
>>>>>>> ISC, VJE, VJC, VJS, XCJC, FC, MJE, MJC, MJS, ITF, VTF, XTF.
><snip>
>>>>>> Everyone has their own idea, see below, based on a variety of amateur
>>>>>> (usually a know-it-all PhD :) curve-fitting techniques...
>>>>> <snip>
>>>>>> ...Jim Thompson
>>>>> All those models have the same problem w/r to reverse emitter current
>>>>> at 25MHz.
>>>>> Looks like CJE is four orders of magnitude higher than BFR93a or
>>>>> BFP405.
>>>>> Correcting this on any of the 2n2222 models fixes it, but I'm not sure
>>>>> how an emitter junction could be expected to exhibit capacitance in
>>>>> the 1E-15 range.
>>>>> RL
>>>>Well, I have been using a 2N222s model with Cje=22 pF. The BFR93 gives >>>>2pF, i.e. one order of magnitude less and the BFP 405 gives 3.7 fF.
>>>>Now it is about time to make some measurements...
>>>>Pere
>>>There is also an issue with CJC, in combination with RB, that defines
>>>the delay and speed of the falling edge of the emitter-follower
>>>rectifier. Capacitance with the same orders of magnitude difference
>>>show up, producing a spike, if significant.
>>>Gummel-Poon BJT modeling is aimed at small-signal representations,
>>>where DC-biased variables are roughly static (even if non-linear).
>>>I've seen this combated with look-up tables, but it's slooooow.
>>Wrong. If you properly extract all the parameters it correctly models
>>everything but deep saturation and injection into substrate. PSpice
>>adds the ability to model that region (used to be useful in TTL days
>>;-); and also provides an alternate model, MEXTRAM.
>Could you identify the parameters that ensure this accuracy?
>Does it include any of those presently missing?
>RL
Gummel-Poon, particularly as implemented in Spice, IS a non-linear
model...
...Jim Thompson
-- | James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | 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 at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
> >> On Mon, 12 Nov 2012 18:40:59 -0500, "Michael A. Terrell"
> >> <mike.terr...@earthlink.net> wrote:
> >> >o pere o wrote:
> >> >> Well, I have been using a 2N222s model with Cje=22 pF. The BFR93 gives
> >> >> 2pF, i.e. one order of magnitude less and the BFP 405 gives 3.7 fF.
> >> >> Now it is about time to make some measurements...
> >> > Wow! Were did you find 2N222s? Obsolete for decades, and damn
> >> >expensive.
> >> Come on! In the Spice catalog, they're really cheap!
> > They were never 'cheap'.
> The Spice ones are. You can't get much cheaper than LTSpice.
You have spice models for '60s vintage three digit transistors?
> On Mon, 12 Nov 2012 09:55:50 +0100, o pere o <m...@somewhere.net> wrote:
>> On 11/12/2012 03:34 AM, legg wrote:
>>> On Sun, 11 Nov 2012 12:17:22 -0500, legg <l...@nospam.magma.ca> wrote:
>>>> On Sat, 10 Nov 2012 22:53:08 +0100, o pere o <m...@somewhere.net> wrote:
>>>>> To make a long story short, I ended up simulating an emitter follower
>>>>> with Qucs. This simulator has some transistor models embedded, but you
>>>>> are able to insert PSpice models and subcircuits if you need more.
>>>>> When you increase input signal level up to the point where the output
>>>>> should clip at zero, one transistor model clips correctly (BFP405, from
>>>>> Qucs) but others not (BFR93a, 2N2222A). The BFR93a model is a PSpice
>>>>> model from the NXP site and I have tried several 2N2222a models (one
>>>> >from Qucs itself, one PSpice model from Zetex and another PSpice model
>>>> >from somewhere): none of these clips at zero although it does at VCC=3.3.
>>>>> Tried the same circuit in LTSpice with the same result. Am I the only
>>>>> one experiencing this? Has anyone got better large-signal models
>>>>> -especially for the BFR93a?
>>>>> Pere
>>>>> At 25MHz, your input signal is using the bipolar transistor as
>>>>> rectifier, clamped by the CB junction.
>>>>> You'd need a lot of accurate reverse and dynamic parameters in your
>>>>> model, to get anything close to reality.
>>>>> The 2n2222a model may be missing (from inspection of popular models)
>>>>> ISC, VJE, VJC, VJS, XCJC, FC, MJE, MJC, MJS, ITF, VTF, XTF.
>>>>> At 25MHz, your input signal is using the bipolar transistor as
>>>>> rectifier, clamped by the CB junction.
>>>>> You'd need a lot of accurate reverse and dynamic parameters in your
>>>>> model, to get anything close to reality.
>>>> Everyone has their own idea, see below, based on a variety of amateur
>>>> (usually a know-it-all PhD :) curve-fitting techniques...
>>> <snip>
>>>> ...Jim Thompson
>>> All those models have the same problem w/r to reverse emitter current
>>> at 25MHz.
>>> Looks like CJE is four orders of magnitude higher than BFR93a or
>>> BFP405.
>>> Correcting this on any of the 2n2222 models fixes it, but I'm not sure
>>> how an emitter junction could be expected to exhibit capacitance in
>>> the 1E-15 range.
>>> RL
>> Well, I have been using a 2N222s model with Cje=22 pF. The BFR93 gives
>> 2pF, i.e. one order of magnitude less and the BFP 405 gives 3.7 fF.
>> Now it is about time to make some measurements...
>> Pere
> BFR93a in the file I have has CJE of 3.2E-15, similar to BFP405. If
> this is altered to 2.2pF, an emitter excursion to -2.5V occurs.
>On 11/12/2012 07:37 PM, legg wrote:
>> On Mon, 12 Nov 2012 09:55:50 +0100, o pere o <m...@somewhere.net> wrote:
>>> On 11/12/2012 03:34 AM, legg wrote:
>>>> On Sun, 11 Nov 2012 12:17:22 -0500, legg <l...@nospam.magma.ca> wrote:
>>>>> On Sat, 10 Nov 2012 22:53:08 +0100, o pere o <m...@somewhere.net> wrote:
>>>>>> To make a long story short, I ended up simulating an emitter follower
>>>>>> with Qucs. This simulator has some transistor models embedded, but you
>>>>>> are able to insert PSpice models and subcircuits if you need more.
>>>>>> When you increase input signal level up to the point where the output
>>>>>> should clip at zero, one transistor model clips correctly (BFP405, from
>>>>>> Qucs) but others not (BFR93a, 2N2222A). The BFR93a model is a PSpice
>>>>>> model from the NXP site and I have tried several 2N2222a models (one
>>>>> >from Qucs itself, one PSpice model from Zetex and another PSpice model
>>>>> >from somewhere): none of these clips at zero although it does at VCC=3.3.
>>>>>> Tried the same circuit in LTSpice with the same result. Am I the only
>>>>>> one experiencing this? Has anyone got better large-signal models
>>>>>> -especially for the BFR93a?
>>>>>> Pere
>>>>>> At 25MHz, your input signal is using the bipolar transistor as
>>>>>> rectifier, clamped by the CB junction.
>>>>>> You'd need a lot of accurate reverse and dynamic parameters in your
>>>>>> model, to get anything close to reality.
>>>>>> The 2n2222a model may be missing (from inspection of popular models)
>>>>>> ISC, VJE, VJC, VJS, XCJC, FC, MJE, MJC, MJS, ITF, VTF, XTF.
>>>>>> At 25MHz, your input signal is using the bipolar transistor as
>>>>>> rectifier, clamped by the CB junction.
>>>>>> You'd need a lot of accurate reverse and dynamic parameters in your
>>>>>> model, to get anything close to reality.
>>>>> Everyone has their own idea, see below, based on a variety of amateur
>>>>> (usually a know-it-all PhD :) curve-fitting techniques...
>>>> <snip>
>>>>> ...Jim Thompson
>>>> All those models have the same problem w/r to reverse emitter current
>>>> at 25MHz.
>>>> Looks like CJE is four orders of magnitude higher than BFR93a or
>>>> BFP405.
>>>> Correcting this on any of the 2n2222 models fixes it, but I'm not sure
>>>> how an emitter junction could be expected to exhibit capacitance in
>>>> the 1E-15 range.
>>>> RL
>>> Well, I have been using a 2N222s model with Cje=22 pF. The BFR93 gives
>>> 2pF, i.e. one order of magnitude less and the BFP 405 gives 3.7 fF.
>>> Now it is about time to make some measurements...
>>> Pere
>> BFR93a in the file I have has CJE of 3.2E-15, similar to BFP405. If
>> this is altered to 2.2pF, an emitter excursion to -2.5V occurs.
I would like to see the Telefunken file, if there ever was one, but
Vishay seems to have divested it's bipolar semiconductors entirely,
since having 'incorporated' their ass.
>I would like to see the Telefunken file, if there ever was one, but
>Vishay seems to have divested it's bipolar semiconductors entirely,
>since having 'incorporated' their ass.
The last Telefunken (Temic) datasheet for bfr93 lists S parameters.
It looks like the Siemens spice model has a typo fF for pF. There's no
way CJC could be three orders of magnitude larger than CJE in the same
part.
>>These are the values used in the LTspice distro.
>>I would like to see the Telefunken file, if there ever was one, but
>>Vishay seems to have divested it's bipolar semiconductors entirely,
>>since having 'incorporated' their ass.
>The last Telefunken (Temic) datasheet for bfr93 lists S parameters.
>It looks like the Siemens spice model has a typo fF for pF. There's no
>way CJC could be three orders of magnitude larger than CJE in the same
>part.
>RL
Here's what I have (from a Kevin Alyward - SuperSpice/Anasoft/Philips
library)...
...Jim Thompson
-- | James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | 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 at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
measuring Vb and Ve. Transistors: 2N2222a and BFR93a.
BFR93a:
Generator is adjusted to Vdc=2.3V and 5Vpp.
At 1 MHz, the emitter signal waveform is a nice trapezoidal signal with a steeper slope when leaving the upper clipping level. The simulator predicts rounded tops and a somewhat upwards sloping bottom.
At 27 MHz the Spice model predicts negative signal excursions. I could not observe them. But if I add some 5-10 pF at the emitter resistance to account for the probe, simulations and reality almost match.
2N2222a:
Generator is adjusted to Vdc=0 and 5Vpp.
At 27 MHz, Spice model predicts sinusoidal signal centered around 0 approx +-2.3. On the scope I see max +1.8 and min -1.5, i.e. there is some loss but the qualitative shape is ok. Of course, this is not what the circuit is expected to do, but indicates the model is ok.
At 1 MHz, Spice model predicts bottom clipping but with positive slope of 1.9V/us. Measurements more or less confirm this.
At 27 MHz, a quite sinusoidal output signal of 4Vpp can be measured adjusting Vdc=1.3. The simulator predicts the same, although with a 4.5Vpp amplitude. So, the model seems ok.
Conclusion:
The Spice models are ok and they do model large signal behavior. It was my error to assume that there could be no negative signal excursions: this is only true at low frequencies. Somehow I thought that 27 MHz was dc for a 5 GHz transistor. But his is not the case for a high input impedance circuit, as JT pointed out.
>>On Tue, 13 Nov 2012 10:59:50 -0500, legg <l...@nospam.magma.ca> wrote:
<snip>
>>>>Strange, I got it directly from NXP >>>>http://www.nxp.com/download/pip/BFR93A/models <snip>
>>>Check out the Seimens model, though:
>>>These are the values used in the LTspice distro.
>>>I would like to see the Telefunken file, if there ever was one, but
>>>Vishay seems to have divested it's bipolar semiconductors entirely,
>>>since having 'incorporated' their ass.
>>The last Telefunken (Temic) datasheet for bfr93 lists S parameters.
>>It looks like the Siemens spice model has a typo fF for pF. There's no
>>way CJC could be three orders of magnitude larger than CJE in the same
>>part.
>>RL
>Here's what I have (from a Kevin Alyward - SuperSpice/Anasoft/Philips
>library)...
This is the same Philips model listed in the LTspice group comparison,
and currntly offered for download from NXP, though a later date is
attributed to the file:
http://tech.groups.yahoo.com/group/LTspice/files/%20Lib/BFR93A/ A ring oscillator sim is offered for 4 model versions.
If the Siemens/Infineon model's CJE is altered from xE-15 to xE-12,
it's performance more closely resembles the other three versions, in
simulation.
>>On Mon, 12 Nov 2012 12:41:46 -0700, Jim Thompson
>><To-Email-Use-The-Envelope-I...@On-My-Web-Site.com> wrote:
>>>On Mon, 12 Nov 2012 14:22:48 -0500, legg <l...@nospam.magma.ca> wrote:
<snip>
>>>>There is also an issue with CJC, in combination with RB, that defines
>>>>the delay and speed of the falling edge of the emitter-follower
>>>>rectifier. Capacitance with the same orders of magnitude difference
>>>>show up, producing a spike, if significant.
>>>>Gummel-Poon BJT modeling is aimed at small-signal representations,
>>>>where DC-biased variables are roughly static (even if non-linear).
>>>>I've seen this combated with look-up tables, but it's slooooow.
>>>Wrong. If you properly extract all the parameters it correctly models
>>>everything but deep saturation and injection into substrate. PSpice
>>>adds the ability to model that region (used to be useful in TTL days
>>>;-); and also provides an alternate model, MEXTRAM.
>>Could you identify the parameters that ensure this accuracy?
>>Does it include any of those presently missing?
>>RL
>Gummel-Poon, particularly as implemented in Spice, IS a non-linear
>model...
>And there's already chit-chat about the Christmas scheduling... we're
>celebrating it on December 29 this year to accommodate the college
>students and the granddaughter already graduated and working.
>And my sensitive mind suspects something coming I didn't expect to
>live to see... that _granddaughter_ announcing her engagement ;-)
>Maybe I'll make it to great-grandfather :-)
> ...Jim Thompson
My suspicions are correct :-)
...Jim Thompson
-- | James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | 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 at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
