How Can I measure MOSFET ro(output resistance), ID(DC current) at LTSpice?

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Oppaya

Joined Apr 16, 2021
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enter image description here
The subject is to make ro=500k, ID=100u by setting VG3,VG4 and W/L of MOSFET.
And I got the exact values from Hand-calculation, and am trying to test it by using LTSpice.
enter image description here
I did make this schematic. and DC currents of two mosfet was around 74uA (I don't know it is right way to measure...)
And the second, I tried to make V/I curve for measuring R values(blue line) It seems that it remarks something meaningful.. but I don't think it is values of output resistance because it is DC resistance...
How can I measure ro(output resistance) and DC current of PMOS-current-source?
 

crutschow

Joined Mar 14, 2008
27,697
Two MOSFETs in series is an odd circuit and not really a current source.
You can put them in parallel as a current-mirror current-source.

Below is the schematic of an N-MOSFET current mirror:

1619875247715.png
 

Papabravo

Joined Feb 24, 2006
16,773
Are you familiar with the .meas(ure) spice command, and do you know where to look for the results?
If not then look firs in the LTspice help file. Read it carefully, then read it again even more carefully.
 

Thread Starter

Oppaya

Joined Apr 16, 2021
8
Are you familiar with the .meas(ure) spice command, and do you know where to look for the results?
If not then look firs in the LTspice help file. Read it carefully, then read it again even more carefully.
I did accomplish my work by using DC transfer function(.tf). I'd look LTspice help file related to .meas . Thank you!
 
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