open-source-silicon.dev

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)

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.