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Printing magnitude in "AC" analysis (Read 2839 times)

Venkateshr Junior Member Offline Posts: 10 Bangalore	Printing magnitude in "AC" analysis May 31^st, 2007, 3:52am hello , I want my verilogA block to recognize the input vsin source magnitude but it is not doing so.what is the reason ? I am just using $display("%r",V(Vin)); but it is saying 0.0000. However if I give some dc voltage to the vsin it is printing that. Is there any way to get the magnitude ? Please help me guys.
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Geoffrey_Coram

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Re: Printing magnitude in "AC" analysis
Reply #1 - Jun 1^st, 2007, 9:13am

You can't get the ac magnitude from within the verilog-a module. Only the simulator knows the ac small-signal quantities. The modules have to evaluate their operating points at the dc voltages, but then the simulator takes the dc currents and conductances and builds the small-signal equivalent circuit. The simulator doesn't evaluate the modules when solving the small-signal circuit.

If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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Venkateshr

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Re: Printing magnitude in "AC" analysis
Reply #2 - Jun 1^st, 2007, 11:11pm

Thanks. I thought the same.But desperately I want to build a frequenncy meter which works in ac that is why trying this sorts of things.

whether the ac_stim function will work inside veriloga in �correspondence to external ac frequency sweep ? I mean whether the freq. of ac_stim will be same as external frequency �:-/ ?

is there any way to build a frequency meter which works in ac & is it possible to measure the ac magnitude �so that amnt of peaking & 3db mmt, drop at specified frequency etc etc can be automated instead of manual mmt?

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Ken Kundert Global Moderator Offline Posts: 2386 Silicon Valley	Re: Printing magnitude in "AC" analysis Reply #3 - Jun 2^nd, 2007, 10:48am You would need to use a results processing language to automate the measurement of peaking and bandwidth. Something like MDL if you are using Spectre. -Ken
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