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Plotting Gm vs Vgs in cadence IC6.1.6

Casp

Hi,

I want to plot gm of a transistor vs vin. Basically gm of a differential pair with input.

I read it on this forum where Andrew Beckett suggested to make a file and write save M1:gm and then add it model libraries and run dc-sweep analysis.

If I try to do so it gives me a warning 'M1: Does not have a terminal named `gm''.

If I look at netlist file input.scs then it is indeed using terminal e.g. 1,2,3 to save the waveform 

Is anything has changed ? 

How I can now plot gm of a transistor in dc-sweep analysis?

Regards,

Kamran 

Parents

  • Hi Kamran,

    My guess is that the model for M1 is actually a subckt model (it's not a direct transistor instance), and so there's no transistor called M1. It's probably called M1.Mnn (or something like that) and so you'd need to save M1.Mnn:gm (or whatever). I suggest you just do a DC operating point simulation (don't do a DC sweep) initially, and then look in the results browser to see if there's hierarchy under the device M1 (or look in the model files to figure it out yourself).

    Most likely, you're just asking to save the wrong thing...

    Regards,

    Andrew.

Reply

  • Hi Kamran,

    My guess is that the model for M1 is actually a subckt model (it's not a direct transistor instance), and so there's no transistor called M1. It's probably called M1.Mnn (or something like that) and so you'd need to save M1.Mnn:gm (or whatever). I suggest you just do a DC operating point simulation (don't do a DC sweep) initially, and then look in the results browser to see if there's hierarchy under the device M1 (or look in the model files to figure it out yourself).

    Most likely, you're just asking to save the wrong thing...

    Regards,

    Andrew.

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