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purplewolf

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Transient Simulation issue
Jul 29^th, 2010, 1:14pm

I have a transient simulation for 100ns..it took about 10 minutes..
I wonder whether

1) the behaviour in first 20ns is related to the transient state of the circuit and spectre is trying to converge
2)After 20ns Spectre converges and find the steady state solution..
Am i thinking in the right direction?

Should i ignore whatever happens in the first 20ns and consider trust the waveforms aound let say 80ns or 90ns??
I also wonder whether is unstability in the circuit??

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sheldon

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Re: Transient Simulation issue
Reply #1 - Jul 29^th, 2010, 9:14pm

Purplewolf,

� Don't think that it is a convergence issue, just think it takes a little
time to settle. Try an experiment, save the transient state at 100ns,
then restart the simulation from 100ns and run to 200ns and see if
the results are stable.

� � � � � � � � � � � � � � � � � � � � � � � � � � � � �Best Regards,

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � Sheldon

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pancho_hideboo

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Re: Transient Simulation issue
Reply #2 - Aug 7^th, 2010, 9:57pm

purplewolf wrote on Jul 29^th, 2010, 1:14pm:

I also wonder whether is unstability in the circuit??

You can not judge it from your simulation results.

You have to verify it by various methods.

http://www.designers-guide.org/Forum/YaBB.pl?num=1243078889
http://www.designers-guide.org/Forum/YaBB.pl?num=1234428781/7#7
http://www.designers-guide.org/Forum/YaBB.pl?num=1218635777/5#5
http://www.designers-guide.org/Forum/YaBB.pl?num=1255834027/14#14
http://www.designers-guide.org/Forum/YaBB.pl?num=1268385779/1#1

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« Last Edit: Aug 8^th, 2010, 12:51am by pancho_hideboo »

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purplewolf

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Re: Transient Simulation issue
Reply #3 - Aug 10^th, 2010, 3:23am

in the first 20ns...
also sometimes the current or voltage waveform is amplitude modulated..is that indicationb of low frequency instability as device has lots of gain and stability issues at low frequency...
i wonder if its possible to get an idea of stability issues from the transient simulation apart from circles and k factor..

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