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Simulators >> Circuit Simulators >> AC analysis in Ansoft Designer with Nexxim
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Message started by carl_chao on Dec 1^st, 2005, 9:25am

Title: AC analysis in Ansoft Designer with Nexxim
Post by carl_chao on Dec 1^st, 2005, 9:25am

Hi,

I'm trying to do a simple opamp (with MOSFETs and resistors) spice-styled AC analysis with Nexxim, but cannot get the right result. It seems that I need to use the Linear Network Analysis to do that, but exactly how, and how about the input and output port impedance, and what should I plot in its simulation results (the S21 parameter?)? Is there an old way in Nexxim like in Cadence or other spice simulator to do the AC analysis?

Thanks in advance!

CC

Title: Re: AC analysis in Ansoft Designer with Nexxim
Post by vborich on Dec 2^nd, 2005, 8:36pm

Some simulators, especially the microwave-centric ones, do not offer classical AC analysis. I've never used Nexxim, but I am aware of others that don't.

You can compute all the quantities you need from multi-port matrix parameters, either directly or as functions of the matrix elements.

For example, the open-circuit voltage gain of your opamp is an element of the ABCD a.k.a chain matrix, if Nexxim lets you compute it.

Except for the S-parameters, most other network descriptions are port impedance-independent, so it really doesn't matter what you specify.

Vuk