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how to find out gm and its derivatives at perticular frequency

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sureshnaidu

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how to find out gm(transconductance) and its derivatives at perticular frequency?.Iam using cadence tool and spectrerf simulator.please respond..............
 

Re: how to find out gm and its derivatives at particular frequency

sureshnaidu said:
how to find out gm(transconductance) and its derivatives at perticular frequency?.
Click to expand...

By running an AC analysis and plotting gm (and its derivatives) vs. frequency.
 
Re: how to find out gm and its derivatives at particular frequency

erikl said:
By running an AC analysis and plotting gm (and its derivatives) vs. frequency.
Click to expand...

i don't have gm and (its derivatives ) options in AC analysis.
 
Re: how to find out gm and its derivatives at particular frequency

\[gm = \frac {\partial{I_D}}{\partial{V_{GS}}} \] . Use the calculator!
 
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    saranasr

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in HSPICE, we use LX7(M1) to plot the gm, where M1 is the MOS instance that you wanted...
 

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Re: how to find out gm and its derivatives at particular frequency

erikl said:
\[gm = \frac{\partial I_D}{\partial V_G_S} \] . Use the calculator!
Click to expand...

HI,

how to do \[gm = \frac{\partial I_D}{\partial V_G_S} \] in calculator???
 
Re: how to find out gm and its derivatives at particular frequency

Hi erikl, I may not say clearly: whay I want is \[\frac{\partial I_D}{\partial V_G_S} \] over frequency. by using deriv() function, how to plot in frequency domain?
 

Re: how to plot gm vs. frequency

See my first answer above. This works for one single operating point Ids=f(Vgs) only. If you want this for several Vgs operating points, you can sweep it (use "Parametric Analysis").
 

sureshnaidu said:
how to find out gm(transconductance) and its derivatives at perticular frequency?.Iam using cadence tool and spectrerf simulator.please respond..............
Click to expand...

In small signal analysis by definition you have
id=gm . vgs
hence
gm(f) = id(f)/vgs(f)

no derivatives involved yet. Once you have the above result, you can calculate the derivative of gm wrt f using the deriv() function in the calculator
 

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