Forums

LTSpice: Slow on noise sims with foreign opamps

Started by Joerg January 4, 2013
Folks,

Yahoo has made the sign-in procedure so onerous (can't get in anymore)
that I'll ask here instead of the LTSpice group:

I want to do some noise simulations, for example with a TI opamp in
there. Loading the complete model it spends forever in the stepping
phase, then pseudo-damped analysis and whatnot.

Is there any way this can be sped up? All I need to see is ballpark
where the 1/f knees will be with various circuit constellations, input
current noise, input voltage noise, stuff like that.

-- 
Regards, Joerg

http://www.analogconsultants.com/
On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid>
wrote:

>Folks, > >Yahoo has made the sign-in procedure so onerous (can't get in anymore) >that I'll ask here instead of the LTSpice group:
What? You refused to identify yourself with a Username and Password ?>:-} And there is an E-mailed Digest... quite useful.
> >I want to do some noise simulations, for example with a TI opamp in >there. Loading the complete model it spends forever in the stepping >phase, then pseudo-damped analysis and whatnot.
Sounds like you don't know how to do a dotAC plus Noise analysis. Which OpAmp?
> >Is there any way this can be sped up? All I need to see is ballpark >where the 1/f knees will be with various circuit constellations, input >current noise, input voltage noise, stuff like that.
...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.
Jim Thompson wrote:
> On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid> > wrote: > >> Folks, >> >> Yahoo has made the sign-in procedure so onerous (can't get in anymore) >> that I'll ask here instead of the LTSpice group: > > What? You refused to identify yourself with a Username and Password > ?>:-} >
I did ID myself. But now they slapped on a stupid "captcha". Which promptly resulted in "Can't identify the machine bla-bla-bla, followed by a challenge question to which they cannot have the answer. IOW, they are on the path of oversophisticating the Yahoo groups to death.
> And there is an E-mailed Digest... quite useful. >
But can you probably can't ask questions via that.
>> I want to do some noise simulations, for example with a TI opamp in >> there. Loading the complete model it spends forever in the stepping >> phase, then pseudo-damped analysis and whatnot. > > Sounds like you don't know how to do a dotAC plus Noise analysis. >
I don't do noise analyses much, that's usually done on the bench here but in this case it should be sim'd.
> Which OpAmp? >
OPA4140. [...] -- Regards, Joerg http://www.analogconsultants.com/
On Fri, 04 Jan 2013 11:23:55 -0800, Joerg wrote:

> Folks, > > Yahoo has made the sign-in procedure so onerous (can't get in anymore) > that I'll ask here instead of the LTSpice group: > > I want to do some noise simulations, for example with a TI opamp in > there. Loading the complete model it spends forever in the stepping > phase, then pseudo-damped analysis and whatnot. > > Is there any way this can be sped up? All I need to see is ballpark > where the 1/f knees will be with various circuit constellations, input > current noise, input voltage noise, stuff like that.
You can try to email to ltspice@yahoogroups.com but the email has to come from your yahoo email id or from the id where you get the email digest or individual messages. Or, just create a new account on yahoo and sign up for the ltspice group again. If all else fails I'll post this for you but you know the first thing they are going to want is an example circuit. -- Chisolm Republic of Texas
On Fri, 04 Jan 2013 12:21:05 -0800, Joerg <invalid@invalid.invalid>
wrote:

>Jim Thompson wrote: >> On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid> >> wrote: >> >>> Folks, >>> >>> Yahoo has made the sign-in procedure so onerous (can't get in anymore) >>> that I'll ask here instead of the LTSpice group: >> >> What? You refused to identify yourself with a Username and Password >> ?>:-} >> > >I did ID myself. But now they slapped on a stupid "captcha". Which >promptly resulted in "Can't identify the machine bla-bla-bla, followed >by a challenge question to which they cannot have the answer.
Do we live in the same universe? I've never experienced that.
> >IOW, they are on the path of oversophisticating the Yahoo groups to death. > > >> And there is an E-mailed Digest... quite useful. >> > >But can you probably can't ask questions via that.
Sure you can. I participate several times a week. They actually discuss engineering there >:-}
> > >>> I want to do some noise simulations, for example with a TI opamp in >>> there. Loading the complete model it spends forever in the stepping >>> phase, then pseudo-damped analysis and whatnot. >> >> Sounds like you don't know how to do a dotAC plus Noise analysis. >> > >I don't do noise analyses much, that's usually done on the bench here >but in this case it should be sim'd. > > >> Which OpAmp? >> > >OPA4140. > >[...]
Set-up how? Feedback, bias, supplies, etc. ...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.
Jim Thompson wrote:
> On Fri, 04 Jan 2013 12:21:05 -0800, Joerg <invalid@invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid> >>> wrote: >>> >>>> Folks, >>>> >>>> Yahoo has made the sign-in procedure so onerous (can't get in anymore) >>>> that I'll ask here instead of the LTSpice group: >>> What? You refused to identify yourself with a Username and Password >>> ?>:-} >>> >> I did ID myself. But now they slapped on a stupid "captcha". Which >> promptly resulted in "Can't identify the machine bla-bla-bla, followed >> by a challenge question to which they cannot have the answer. > > Do we live in the same universe? I've never experienced that. >
Tried numerous times, always the captcha. Those things are nasty but after four tries it let me past the virtual bouncer. Wot a pain.
>> IOW, they are on the path of oversophisticating the Yahoo groups to death. >> >> >>> And there is an E-mailed Digest... quite useful. >>> >> But can you probably can't ask questions via that. > > Sure you can. I participate several times a week. They actually > discuss engineering there >:-} >
I know they do. But so far I haven't figured out a way inside without that dreaded Yahoo GUI. So where's the back door and how many knocks?
>> >>>> I want to do some noise simulations, for example with a TI opamp in >>>> there. Loading the complete model it spends forever in the stepping >>>> phase, then pseudo-damped analysis and whatnot. >>> Sounds like you don't know how to do a dotAC plus Noise analysis. >>> >> I don't do noise analyses much, that's usually done on the bench here >> but in this case it should be sim'd. >> >> >>> Which OpAmp? >>> >> OPA4140. >> >> [...] > > Set-up how? Feedback, bias, supplies, etc. >
Essentially I've plopped the whole Texas model in there. Right now supplied +/-5V, for the test stripped back to a follower with just 10k OUT to IN-, IN+ to 0V (ground). With any LTC models it zips right through even with complicated stuff around them, as usual. -- Regards, Joerg http://www.analogconsultants.com/
Joe Chisolm wrote:
> On Fri, 04 Jan 2013 11:23:55 -0800, Joerg wrote: > >> Folks, >> >> Yahoo has made the sign-in procedure so onerous (can't get in anymore) >> that I'll ask here instead of the LTSpice group: >> >> I want to do some noise simulations, for example with a TI opamp in >> there. Loading the complete model it spends forever in the stepping >> phase, then pseudo-damped analysis and whatnot. >> >> Is there any way this can be sped up? All I need to see is ballpark >> where the 1/f knees will be with various circuit constellations, input >> current noise, input voltage noise, stuff like that. > > You can try to email to ltspice@yahoogroups.com but the email has to > come from your yahoo email id or from the id where you get the email > digest or individual messages. Or, just create a new account on > yahoo and sign up for the ltspice group again. > > If all else fails I'll post this for you but you know the first > thing they are going to want is an example circuit. >
I've got the circuit working, it's just that it doesn't seem to like Texas models. No, no, not those :-) -- Regards, Joerg http://www.analogconsultants.com/
On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid>
wrote:

>Folks, > >Yahoo has made the sign-in procedure so onerous (can't get in anymore) >that I'll ask here instead of the LTSpice group: > >I want to do some noise simulations, for example with a TI opamp in >there. Loading the complete model it spends forever in the stepping >phase, then pseudo-damped analysis and whatnot. > >Is there any way this can be sped up? All I need to see is ballpark >where the 1/f knees will be with various circuit constellations, input >current noise, input voltage noise, stuff like that.
Bwahahahahahaha! The OPA4140 Spice model provided by TI is what gives model-makers a bad name... the sort of model you get when you take a PhD with no hands-on-lab experience and sit them down in front of a simulator. I don't think I've ever seen such a badly constructed model before. No wonder it takes forever to converge. ...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.
Jim Thompson wrote:
> On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid> > wrote: > >> Folks, >> >> Yahoo has made the sign-in procedure so onerous (can't get in anymore) >> that I'll ask here instead of the LTSpice group: >> >> I want to do some noise simulations, for example with a TI opamp in >> there. Loading the complete model it spends forever in the stepping >> phase, then pseudo-damped analysis and whatnot. >> >> Is there any way this can be sped up? All I need to see is ballpark >> where the 1/f knees will be with various circuit constellations, input >> current noise, input voltage noise, stuff like that. > > Bwahahahahahaha! The OPA4140 Spice model provided by TI is what gives > model-makers a bad name... the sort of model you get when you take a > PhD with no hands-on-lab experience and sit them down in front of a > simulator. > > I don't think I've ever seen such a badly constructed model before. No > wonder it takes forever to converge. >
Kind of my hunch, but I hadn't thought it was this bad :-( Burr-Brown used to be a pretty good bunch of engineers, real hands-on guys. Looking at the bright side it did manage to heat my office by one degree Fahrenheit over lunch. -- Regards, Joerg http://www.analogconsultants.com/
On Fri, 04 Jan 2013 14:56:52 -0800, Joerg <invalid@invalid.invalid>
wrote:

>Jim Thompson wrote: >> On Fri, 04 Jan 2013 11:23:55 -0800, Joerg <invalid@invalid.invalid> >> wrote: >> >>> Folks, >>> >>> Yahoo has made the sign-in procedure so onerous (can't get in anymore) >>> that I'll ask here instead of the LTSpice group: >>> >>> I want to do some noise simulations, for example with a TI opamp in >>> there. Loading the complete model it spends forever in the stepping >>> phase, then pseudo-damped analysis and whatnot. >>> >>> Is there any way this can be sped up? All I need to see is ballpark >>> where the 1/f knees will be with various circuit constellations, input >>> current noise, input voltage noise, stuff like that. >> >> Bwahahahahahaha! The OPA4140 Spice model provided by TI is what gives >> model-makers a bad name... the sort of model you get when you take a >> PhD with no hands-on-lab experience and sit them down in front of a >> simulator. >> >> I don't think I've ever seen such a badly constructed model before. No >> wonder it takes forever to converge. >> > >Kind of my hunch, but I hadn't thought it was this bad :-( > >Burr-Brown used to be a pretty good bunch of engineers, real hands-on guys. > >Looking at the bright side it did manage to heat my office by one degree >Fahrenheit over lunch.
Hmmmmmm? Maybe cockpit error? In PSpice, Q-point found as fast as you can blink: **** 01/04/13 17:12:37 ******* PSpice 15.7.0 (July 2006) ****** ID# xxxxxxxx * * C:\Projects\Expments\OpAmps\OPA4140.sch **** JOB STATISTICS SUMMARY ****************************************************************************** Total job time (using Solver 1) = .27 <<<<<<<<<<< See... http://www.analog-innovations.com/SED/OPA4140_Q-Point.pdf What set-up do you want? Noise info for what frequency range? ...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.