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Junbeom Park

04/26/2023, 6:08 AM
hi. How can I measure transconductance(gm) of mosfet? I coded like below. but it was only ZERO.
I want to use Gm/Id methodology. so I am trying to make techplots(Gm/Id, ft, ... etc)
a

Akira Tsuchiya

04/26/2023, 2:18 PM
I guess, the reason is that the transistor is in a subckt. In the netlist, the transistor M1 is defined like
XM1 net2 net 1 ... nfet_03v3 ...
and the subckt
nfet_03v3
is defined in the library sm141064.ngspice. In the definition of
nfet_03v3
, transistor is
m0
. So I tried @xm1.m0[gm], but it didn't work... I am not sure this is the best way, but I use
deriv
to calculate gm = dId/dVgs. Attached is my way to plot gm/id.
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