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Re-use PSS results to run PAC (Read 196 times)
Marios
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Re-use PSS results to run PAC
Sep 20th, 2022, 8:25am
 
Hello guys,

I have a question with regards to PSS and PAC. Assuming a PSS has just finished, can I somehow run a PAC without re-running PSS? And how would I do that?

Best regards
Marios
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Horror Vacui
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Re: Re-use PSS results to run PAC
Reply #1 - Sep 20th, 2022, 8:45am
 
There is an option to write the periodic operation point into a file in the PSS analysis, and there must be an option to load this file in for PAC analysis. I've never tried it, but it should work. It is analogous to how the DC/AC pair would work.

I hope it helps. I can't check the exact option right now, and I thought you would appreciate such a vague answer, if it points you into the right direction.
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Marios
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Re: Re-use PSS results to run PAC
Reply #2 - Sep 20th, 2022, 9:13am
 
Yes thanks a lot. However, once the PSS is done, assuming I had not selected the option for producing the periodic op point into a file I guess the results are lost right?

Marios
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Andrew Beckett
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Re: Re-use PSS results to run PAC
Reply #3 - Dec 30th, 2022, 7:12am
 
The pss parameter in question is writepss. The idea is that to re-use this you run another pss (followed by pac) where you use the readpss parameter to point to the same file. If nothing changed in the circuit or conditions, then you can make it faster by using the finitediff=no parameter setting on both the first and second pss analyses - this avoids a refinement step which sometimes can take significant effort.

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However, once the PSS is done, assuming I had not selected the option for producing the periodic op point into a file I guess the results are lost right?


If you'd not run the first pss with writepss, then that's correct - you have to run again from scratch (there's no data for it to resume from, so it's not exactly surprising that this would be the case).

Andrew
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Ken Kundert
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Re: Re-use PSS results to run PAC
Reply #4 - Dec 30th, 2022, 11:24pm
 
Perhaps this is obvious, but the above suggestions are only needed if Spectre terminates.  It is possible to run a single PSS analysis and many periodic small signals analyses in the same run, each of which will use the periodic operating point computed by the previous PSS analysis.

Due to limitations in ADE you can only run one analysis of each type in a single run.  But if you run Spectre directly on the command line, you can run any number of any type of analysis.  So you can run a PSS analysis, then some periodic small signals analyses, then another PSS analysis, them more periodic small-signal analyses, etc.

-Ken
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