iteration limit reached: another numb noob Q

Onvinyl · 9th March 2006, 09:05 AM

Hi,

when simulating my circuit in ltspice it works ok with 'universal opamp' model. if I use a certain model, be it from LT or a third party, I get an error saying: 'iteration limit reached'. The circuit works in reality.
Why is that, and how to cope?
Rüdiger

lineup · 9th March 2006, 09:20 AM

maybe you should build the thing ....

then is REALLY working audio circuit

Onvinyl · 9th March 2006, 09:31 AM

He lineup,
what a worthwhile advice

It *is* build in reality, and not working in sim (anyway, better than the other way round). I did so to check what happens to happen both in sim and reality if I change something.

The sim works now, I replaced *all* opamps with their dedicated models. It seems you can't mix both universal and specific models, of course, I don't know if this is true in all cases.
Rüdiger

Edit: Wrong! It seems to work only randomly. If I change anything (e.g. add a parallel cap to Rf), then I get the error warning again

Geek · 9th March 2006, 09:55 AM

Hi,

That's a common Spice engine error and opamp simulations are the worst offenders. Can mean a myriad of things from too complex of a circuit or signal to not enough info to make the calculations.

I've found that sometimes the silliest things can cure it - like varying a resistor by one ohm (99.999K instead of 100K on a feedback resistor for example) and other times it plain won't run.

Can you try another, more co-operative opamp model with similar charcteristics (like a TL072 for an 082)? The real-life difference won't be significant.

Cheers!

9th March 2006, 09:05 AM	#1
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	iteration limit reached: another numb noob Q Hi, when simulating my circuit in ltspice it works ok with 'universal opamp' model. if I use a certain model, be it from LT or a third party, I get an error saying: 'iteration limit reached'. The circuit works in reality. Why is that, and how to cope? Rüdiger

9th March 2006, 09:20 AM	#2
lineup diyAudio Member Join Date: Dec 2005 Location: the north	maybe you should build the thing .... then is REALLY working audio circuit __________________ lineup

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9th March 2006, 09:31 AM	#3
Onvinyl diyAudio Member Join Date: Aug 2002 Location: Germany	He lineup, what a worthwhile advice It is build in reality, and not working in sim (anyway, better than the other way round). I did so to check what happens to happen both in sim and reality if I change something. The sim works now, I replaced all opamps with their dedicated models. It seems you can't mix both universal and specific models, of course, I don't know if this is true in all cases. Rüdiger Edit: Wrong! It seems to work only randomly. If I change anything (e.g. add a parallel cap to Rf), then I get the error warning again

9th March 2006, 09:55 AM	#4
Geek diyAudio Member Join Date: Sep 2004	Hi, That's a common Spice engine error and opamp simulations are the worst offenders. Can mean a myriad of things from too complex of a circuit or signal to not enough info to make the calculations. I've found that sometimes the silliest things can cure it - like varying a resistor by one ohm (99.999K instead of 100K on a feedback resistor for example) and other times it plain won't run. Can you try another, more co-operative opamp model with similar charcteristics (like a TL072 for an 082)? The real-life difference won't be significant. Cheers!

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