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.step in LTspice

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dkumar

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hi,
I am new to LTspice and wanted to know about one specific type of simulation..
I want to characterize a process where i want to plot gm/Id of a transistor by varying Vg (gate voltage)

I used following commands:
.step Vg 0.6 1 0.1
.op

where Vg is the gate voltage and I had a constant Vds tried across drain and source.
But when i look at error log file to see the output of .op command, i just see one set of device parameter values and not 5 (which i expect as i want to simulate 5 times using .step command)

at the same time, i also wonder, if at all i can get 5 set of parameter values, how will i be able to plot them with respect to Vg.

Please help me on this.

thanks
 
Two different ways to make a Curve tracer.
 

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HI,
Thanks for the reply. But, in the plot above, you have shown Id vs. Vg /Vd but i am more interested in plotting the gm of the transistor wrt Id or wrt vg

Is there any way i can plot the device small signal parameter, in LT spice?

thanks
 
Is this what you want? Note the use of "waveform arithmetic" where I used the "add trace" dialog box to add the Gm in Seimens plot. I used a double DC sweep to generate the Id vs Vgs at different values of Vds.
 

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