Cadence question concerning virtuoso design environment

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saruman1983

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Another cadence question

Hi all,

How can I simulate the transconductance of a transistor and generally a circuit vs. frequency in the cadence virtuoso design environment?
 

Re: Another cadence question

Hi

I am not sure if this is what you are after. If I am not mistaken, transconductance of a MOS transistor can be simulated in Cadence by doing a simple Ids/Vgs simulation. Then you open up the calculator and use the "deriv" function on the I/V curve. The output should be a transconductance curve for the transistor.
 

Another cadence question

I do simulation with above method, too.
 

Re: Another cadence question

OK, but what if i want to plot the (overall) transconductance of a MOS transistor (not gm, but Gm) for a common source connection for example? The above method requires a DC sweep, then taking the derivative of the curve to find transconductance. I was wondering if that can be done only with an AC analysis,that is when frequency varies and the parasitics of the transistor force the overall Gm to start decreasing.
 

Re: Another cadence question

plot square root of id VS Vgs(or vgs-vt) and find the slope...
then use the drain current equation.
 

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