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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
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  • 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.

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  • 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.

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