Forums

Bad OpAmp Spice Models?

Started by Jim Thompson September 19, 2013
I'm trying to make a list of OpAmp Spice models that either poorly
model power supply currents, or not at all.

Suggestions, hopefully with details of how they deviate from the real
device, would be appreciated.

Thanks!
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| San Tan Valley, AZ 85142   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 Thu, 19 Sep 2013 09:20:25 -0700, Jim Thompson  
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

> I'm trying to make a list of OpAmp Spice models that either poorly > model power supply currents, or not at all. > > Suggestions, hopefully with details of how they deviate from the real > device, would be appreciated. > > Thanks! > > ...Jim Thompson
Have you ever been bit by a model that didn't show the difference in GBW product for when the device was pulling UP versus when the device was pulling DOWN?
On Thu, 19 Sep 2013 09:57:30 -0700, RobertMacy
<robert.a.macy@gmail.com> wrote:

>On Thu, 19 Sep 2013 09:20:25 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: > >> I'm trying to make a list of OpAmp Spice models that either poorly >> model power supply currents, or not at all. >> >> Suggestions, hopefully with details of how they deviate from the real >> device, would be appreciated. >> >> Thanks! >> >> ...Jim Thompson > > >Have you ever been bit by a model that didn't show the difference in GBW >product for when the device was pulling UP versus when the device was >pulling DOWN?
Was it the GBW that got you or slew rate differences between UP and DOWN? I find it hard to imagine a "modern" OpAmp with significant GBW difference UP or DOWN. Way back in the past I know of fully dual-path designs that could do that. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 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 Thu, 19 Sep 2013 10:10:34 -0700, Jim Thompson  
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

> On Thu, 19 Sep 2013 09:57:30 -0700, RobertMacy > <robert.a.macy@gmail.com> wrote: > >> On Thu, 19 Sep 2013 09:20:25 -0700, Jim Thompson >> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >> >>> I'm trying to make a list of OpAmp Spice models that either poorly >>> model power supply currents, or not at all. >>> >>> Suggestions, hopefully with details of how they deviate from the real >>> device, would be appreciated. >>> >>> Thanks! >>> >>> ...Jim Thompson >> >> >> Have you ever been bit by a model that didn't show the difference in GBW >> product for when the device was pulling UP versus when the device was >> pulling DOWN? > > Was it the GBW that got you or slew rate differences between UP and > DOWN? > > I find it hard to imagine a "modern" OpAmp with significant GBW > difference UP or DOWN. Way back in the past I know of fully dual-path > designs that could do that. > > ...Jim Thompson
I don't think was slew rate limiting but as you said 'dual path' design. quite old something like the CA3130 ?
On Thu, 19 Sep 2013 11:35:58 -0700, RobertMacy
<robert.a.macy@gmail.com> wrote:

>On Thu, 19 Sep 2013 10:10:34 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: > >> On Thu, 19 Sep 2013 09:57:30 -0700, RobertMacy >> <robert.a.macy@gmail.com> wrote: >> >>> On Thu, 19 Sep 2013 09:20:25 -0700, Jim Thompson >>> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>> >>>> I'm trying to make a list of OpAmp Spice models that either poorly >>>> model power supply currents, or not at all. >>>> >>>> Suggestions, hopefully with details of how they deviate from the real >>>> device, would be appreciated. >>>> >>>> Thanks! >>>> >>>> ...Jim Thompson >>> >>> >>> Have you ever been bit by a model that didn't show the difference in GBW >>> product for when the device was pulling UP versus when the device was >>> pulling DOWN? >> >> Was it the GBW that got you or slew rate differences between UP and >> DOWN? >> >> I find it hard to imagine a "modern" OpAmp with significant GBW >> difference UP or DOWN. Way back in the past I know of fully dual-path >> designs that could do that. >> >> ...Jim Thompson > >I don't think was slew rate limiting but as you said 'dual path' design. >quite old > >something like the CA3130 ?
OK. Now I understand. BCML: Before current mirror loads ;-) Resistive pull-ups, current pull-downs. I've found an even better way to model power supply current, much better than yesterday's post (I didn't show the math, but it could be far simpler :-) It even can be tacked onto Spice models that lack any power supply pins. So back to playing, then I'll release an upgraded configurable OpAmp model. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 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 Thu, 19 Sep 2013 09:20:25 -0700, Jim Thompson wrote:

> I'm trying to make a list of OpAmp Spice models that either poorly model > power supply currents, or not at all. > > Suggestions, hopefully with details of how they deviate from the real > device, would be appreciated.
So, you're working on a model for the people who do the "connect a PNP booster to the power supply pin" dodge? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On Thu, 19 Sep 2013 14:08:14 -0500, Tim Wescott
<tim@seemywebsite.really> wrote:

>On Thu, 19 Sep 2013 09:20:25 -0700, Jim Thompson wrote: > >> I'm trying to make a list of OpAmp Spice models that either poorly model >> power supply currents, or not at all. >> >> Suggestions, hopefully with details of how they deviate from the real >> device, would be appreciated. > >So, you're working on a model for the people who do the "connect a PNP >booster to the power supply pin" dodge?
Not specifically for that application. Just generally. Since that seems a common complaint. But I've done that very "dodge" myself. Early '70's, LDO with 2N2907 plus LM741 ;-) Worked a peach EXCEPT I found out that not everyone's 741 was actually the same circuit schematic... I was making hybrids at the time, 741 in chip form. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 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.