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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Currents are not steady in AMS simulator ... why? https://designers-guide.org/forum/YaBB.pl?num=1379689668 Message started by pbennett on Sep 20th, 2013, 8:07am |
Title: Currents are not steady in AMS simulator ... why? Post by pbennett on Sep 20th, 2013, 8:07am I have found that when I plot or measure currents in the AMS simulator that they do not appear to be steady. Why is this? I have simulated several different designs ... mostly simple current mirrors and several other circuit blocks and I do not find that the current in AMS/spectre to be solid number like 10 uA ... instead it will numerically oscillate between 9.9 and 10.1ua in a very unpredictable and unsteady way ... Do I have some accuracy setting wrong ?? Have others seen this behavior before? |
Title: Re: Currents are not steady in AMS simulator ... why? Post by pbennett on Sep 20th, 2013, 10:39am well it seems that just by tightening RELTOLfrom 1e-3 to 1e-5 ... makes a world of difference. I would still be interested if anyone has any additional guidance regarding this issue. The simulator of course runs much slower but at least the answers seem to be correct! |
Title: Re: Currents are not steady in AMS simulator ... why? Post by Ken Kundert on Sep 20th, 2013, 3:24pm Sounds like trapezoidal-rule ringing. Is it a point-to-point ringing? If so, switch the transient integration method to gear2. -Ken |
Title: Re: Currents are not steady in AMS simulator ... why? Post by pbennett on Sep 20th, 2013, 4:50pm Yes it seems to be point to point ringing. I will try your suggestion to move to gear2 method. TNKS :) |
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