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https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> two questions https://designers-guide.org/forum/YaBB.pl?num=1221479087 Message started by tempora on Sep 15th, 2008, 4:44am |
Title: two questions Post by tempora on Sep 15th, 2008, 4:44am Hello, I have two issues and hope somebody can help me solve them. 1. After pss analysis, I choose in ADE: Results -> Direct Plot -> Main Form -> thd -> select a node in the schematic and get a plot of thd on that node. How can it be automated (I need an appropriate formula in corner analysis). When I run all corner simulations and do the same as above I get an error in ciw: "*Error* awvfPlotDoubleWave: not a waveform - nil *WARNING* geEcEventCB: An error occurred while applying 'geEcEventCB' to apply('geEcEventCB '("directPlotForm" "newSelSet" (ptrnum@0xb5ca808) (133 t ((db:226645792 nil)))))" I can't possibly run 1 corner at a time and repeat the clicks... 2. I have a Butterworth filter, Salen-Key topology with a cap inside the feedback loop. I would like to simulate ac analysis for phase margin but I get wrong results in comparison with large signal (tran analysis) step response. I get PM of ~70deg in ac but in transient the overshoot looks like PM is 40-45deg at most. I cut the loop during ac just in front of the opamp (after the cap) so the miller multiplication doesn't apply in this case. I think that is why my results are wrong and my PM is bigger than in reality. Question is how to simulate ac then? What test bench to use to get a PM result corresponding to step response I see in tran? Thank you for your help. Regards, L.S. |
Title: Re: two questions Post by Dipankar on Sep 15th, 2008, 7:32am Hi Tempora, about 2. You can use stability analysis in ADE for more accurate PM measurement. need not cut the loop. With regs., Dipankar. |
Title: Re: two questions Post by Tlaloc on Sep 15th, 2008, 8:28am Regarding #1, at the bottom of the Direct Plot form, there is a button called "Add To Outputs". This adds a new output in ADE, and you can see the code to get the waveform there. It should be a getData function. I personally have not used the PSS thd, but my guess to the code would be getData("nameOfNet" ?result "thd"). This returns the waveform object which the can then manipulate through Ocean. |
Title: Re: two questions Post by tempora on Sep 16th, 2008, 3:59am Hello, Thanks for your replies. - About stb analysis, I've tried it and I get the same results as in my ac analysis with opening/closing the loop. I can live with tran analysis results I guess because I don't think now it is possible to simulate this circuit properly with any small signal analysis. - About thd formula in pss, the aproach mentioned works ok, I get a formula: _drplPssThd(v("/out" ?result "pss_fd") 10000) but it works (prints results) fine only if used in one corner simulation. If I run many corners and try to plot the results I get: *Error* awvfPlotDoubleWave: not a waveform - nil *Error* drfGetWaveformXVec: not a waveform - nil If trying to print: *Error* no value at 1 , please check your entry at 'Print At' form (in one corner simulation it shows thd vs index from 1 to 10) However, when using printvs it shows: *Error* X axis not numbers, can't print a portion of it but prints the results. I guess I can live with that for the moment. But I would like to know how to properly format this formula so that it works with no errors. Any ideas are welcome. Thanks. Regards, L.S. |
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