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transconductance "gm" plot in ic5033

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Full Member level 1
Dec 6, 2005
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i have modified a an opamp that i have designed earlier and included a gm control circuit.

i am trying to make a plot of gm vs. v common mode.

any idea how i can do that in ic5033


I think you can access the transistor parameters such as gm from the calculator.
So you could do a DC sweep of your common mode and plot the gm.
From the Calculator, open the browser. If you did a DC sweep, you will have in the tree:
psf -- dc-op --
Then select the transistor instance and it's gm.

Or you can access more directly by using the "OP" button. Select the transistor and you can choose to plot the gm. It will be displayed as a function of the DC sweep variable.

Hope it answer your question.

thank you skal81 for your reply...

i tried both ways as described, but i get straight line for gm.

the x axis sweep is not similar to the dc sweep variable which i am using for the dc can't be constant.

i set up the simulation by choosing dc analysis and then selected compenent parameters and then i choose the ac source.....i choose the "dc" parameter to sweep from -.9v to .9v.....and did all the rest as u said......but i am getting a constant value with an x axis extending from 0 to 10.

maybe i am doing a wrong dc sweep.......
your help is much appreciated.

Strange I though it would work with a DC sweep. In that case try with a DC parametric analisys.
Save the DC point. Do the parametric analisys on your common mode voltage and plot the gm. You should have several points and the x-axis should be the DC voltage. Then with the calculator choose "familly" and "value" to plot the gm as a function of the parametric sweep variable.


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A way to do this is discussed here:


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