This is my PMOS circuit.


This graph obtained using LTSPICE. The graph is Isd VS Vsd




I am trying to make it look like the one above but when I sweep it from vsd 0 to -3 with a increment value of -0.01 , it becomes one straight line.This is what I mean.


Did I do anything wrong? I am still quite new to LTspice

 

Connect the ground symbol to the positive connection of vsd instead of the negative connection.

 

Hi I have changed it but it is still the same.

 

I would also like to check if circuit connection is correct in LTSPICE? (I believe it is correct)
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I am using this circuit for PMOS parameter extraction

 

Your polarity is reversed for Vsd.
You have the minus connected to the drain and then you have a minus for the parameter which gives a plus voltage on the drain.

Below is an example showing the plot as you wanted.

 

Hi. Thank you very much for your help.
I am wondering in my original circuit , when I set the voltage to negative , wont it reverse the polarity of vsd and vsg? but it doesn't produce the result i want.

 

Your circuit exactly as in post #1 will give you the wanted result if you left-click the horizontal axis of the plot and set the Quantity Plotted value to -Vsd.

 

I showed you polarities that work in post #5.
Why then did you invert the sources in post #6 , which inverts the polarities?

If you specify a positive voltage for a source then the (+) output will be positive with respect to the (-) output
If you specify a negative voltage for a source then the (+) output will be negative with respect to the (-) output.