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Plotting Gm vs Vgs for different values of Vbs

wgtkan
I would like to plot Gm vs. Vgs for different value of Vbs.

Here is what I did. I performed DC sweep on Vgs and then plotted the drain current vs Vgs and then carried out derivative of ID with respect to VGS using the calculator, i.e derv(IS(drain)) to obtain GM. Then performed a parametric analysis of different values of Vbs.

Then when I did hand calculation, the result doesn’t match.

I read on this forum that first I have to do parametric analysis of Vgs and then go to ADE and tools > result browser >dc OPInfo then plot gm but it only plots one Gm vs Vgs not at different Vbs. What am I doing wrong?

I have found a tedious method where I plot Gm vs Vgs for different values of Vbs by plotting them one by one meaning I plot Gm vs Vgs at one value of Vbs and then add it to the table, then I do the same for the next.

My version is IC6.1.6-64b.500.2.1
  • Andrew Beckett

    You could directly get the gm from the transistor, which doesn't get saved during a swept analysis (e.g. dc sweep or transient). So create an include file called (say) "save.scs" (make sure you have a .scs suffix) containing:

    save M1:gm

    (note that the M1 should be your transistor name). Include this via Setup->Model Libraries.

    Then do a dc sweep where you sweep Vbs. And a parametric analysis around that where you sweep Vgs. You can then go to the results browser, and for the dc analysis (not dcOpInfo) plot M1:gm.

    Andrew.

  • wgtkan

    Dear Andrew:

     I created an include file using a text editor in my case (gedit) and saved is as save.scs which contains save T1:gm the name of my transistor is T1.

     

    I included this in ADE via Setup-> Model Libraries. First I did a dc sweep of Vgs from 0 to 1.5 in a linear step Mode of total 100 points. Then I did and a parametric analysis of

    values: Vbs1=-1, Vbs2=-0.75, Vbs3 = -0.5, Vbs4 = -0.25, and Vbs5 = 0. Then I went to ADE->Tools->Results browser->dc->T1/gm -> plot.

    I got it.

     

    Thank you very much indeed.

     

  • FormerMember
    FormerMember

    Dear Andrew,

    I have tried to plot gm out of a DC sweep analysis using this method but without success. Here is what I've done:

    create an .scs file with the statement "save M0:gm" (also tried with "save M0:all")

    Included this file into my ADE design via  Setup -> Model libraries

    run the simulation and look at the Results Browser (Tools -> Result Browser): the dc tab shows only voltages and currents but not the parameters (gm and others)

    I have also tried to include the file via Setup -> Simulation files -> Definition files (or tried both) but with no success

    What am I doing wrong?

    Thanks

  • fatcat1206
    Hi Maaz

    I experience the similar situation once, and it turned out to be the structure of the model.
    For some processes, the model files have been tuned by the modeling group inside my company.
    They add one wrapper around the original model to improve accuracy, or do something they need.

    Thus for the save command, this extra layer should be introduced.
    In my case "save M0.m1:gm".

    You may consult the modeling group in your company to see whether this situation is applied to you.

    Best Regards

    Yi

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