how to determine the channel length modulation coefficient?

[carlson]

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!!!

 

[samuel]

channel length modulation r0

you may search "lamda simulation" using google.

 

[pra]

lambda channel length modulation

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

 

[Steven De Bock]

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!!

 

[archillios]

channel length modulation

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

 

[Steven De Bock]

channel length modulation

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

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.

 

[husseinadel]

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)