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how to determine the channel length modulation coefficient?

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carlson

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channel length modulation coefficient

Hi all,
There is no λ(channel length modulation coefficent) in the model file. And λ need to be known in the hand calculation. How to obtain the λ? Please help!!!
 

channel length modulation r0

you may search "lamda simulation" using google.
 

lambda channel length modulation

or u can go for spice documentation where u can find equation for that
 

channel length modulation, lambda

What I did for determining lambda is to determine the slope of the IDvsVDS curve of the transistor in saturation. Now, draw a line through a point of the IDvsVDS curve with the determined slope and determine the intersection with the ID = 0 curve. This results in the point (0, -1/lambda).

This is easily seen from the next level 1 model equation for a transistor in saturation:
ID = 1/2*mu*Cox*W/L*(VGS-VT)^2*(1+lambda*VDS).

lambda is function of L and VGS, so their might be some averaging involved.

Have fun simulating!!
 
channel length modulation

allen said, lamda equations has no practical meaning, deviate from experiments too far.
 

channel length modulation

archillios said:
allen said, lamda equations has no practical meaning, deviate from experiments too far.
Click to expand...

It's true, deviations from experiments aren't very accurate. Although lambda is a very common parameter for equations in gain estimation of an opAmp. So lambda does have a practical meaning.

If you have a better idea and more accurate means to determine small signal output impedances, feel free to share your knowledge.
 

what is modulation coefficient

well ,, you can make sweep by simulation ,,and measure the slope of drain current in the saturation region,, this vakue will be 1/ro and ro=1/(lamda*Id)
 

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