how to find out gm and its derivatives at perticular frequency

[sureshnaidu]

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

 

[erikl]

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

how to find out gm(transconductance) and its derivatives at perticular frequency?.

By running an AC analysis and plotting gm (and its derivatives) vs. frequency.

 

[sureshnaidu]

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

By running an AC analysis and plotting gm (and its derivatives) vs. frequency.

i don't have gm and (its derivatives ) options in AC analysis.

 

[erikl]

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

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

 

[leehying]

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

 

[noahsoon]

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

\[gm = \frac{\partial I_D}{\partial V_G_S} \] . Use the calculator!

HI,

how to do \[gm = \frac{\partial I_D}{\partial V_G_S} \] in calculator???

 

[erikl]

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

how to do \[gm = \frac{\partial I_D}{\partial V_G_S} \] in calculator?

 

[noahsoon]

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?

 

[erikl]

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").

 

[dgnani]

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

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