Simulation of CS stage with LTC Spice

Thread Starter

Dar89

Joined Jan 9, 2012
2
Hello, I have some difficulties with spice simulation. I want simulate the input-output characteristic of a common source stage, with diode-connected load. My problem arises because the result of simulation is different from the characteristic (found on every book :) ) of a common source stage, with diode-connected load. In particoular, from the simulation, i see that the device NMOS amplifier, conducts even if its Vgs<Vth (the current in the simulation has a very great magnitude, so i don't think it's a current of weak inversion). Is this a problem of model of device?I attach a pdf with some images. The model i've used is the follow:
.MODEL nfet NMOS(LEVEL=1, KP=50u, VTO=0.7, LAMBDA=0.01,
+ GAMMA=0.5, PHI=0.7, TOX=15E-9,
+ CJ=4E-4, CJSW=1E-10, MJ=0.5, MJSW=0.5, PB=0.9,
+ CGSO=2.5E-10, CGDO=2.5E-10, CGBO=2.5E-10)
Can you help me? Thanks.

P.S. Excuse me for my english. :D
 

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gootee

Joined Apr 24, 2007
447
It looks like you first need to right-click on those NMOS devices and pick a "real" device from the list of available devices.
 

Ron H

Joined Apr 14, 2005
7,014
It looks like you first need to right-click on those NMOS devices and pick a "real" device from the list of available devices.
You can't pick a "real" part for a 4-pin MOSFET.
What he does need to do is right-click on them and change the model names from NMOS to nfet, which is his model name.
 
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