People will try to 'design' the Vth with respect to Vdd value. Example for logic design.

Thanks a lot, sir for your response T Thammi Reddy

Sir one thing more. As I am working on nanoscale technology nodes, I have taken MOSFET models from predictive technology model(ptm.asu.edu) for 32nm technology. Can we know the value of the channel length modulation(lambda) parameter for a particular technology node.?

Dear Amoldeep Singh ,

T Thammi Reddy already wrote sufficient explanations, especially related with the threshold voltage.

I want to add my comment about "lambda".

Channel length modulation (CLM) effect is represented with a fixed lambda for hand analysis models (simplest models), but in reality CLM behavior it is not as simple as that. The effect depends on many parameters, especially on the channel length.

The simplest "lambda" model assumes an almost fixed slope of ID-VDS curve which is not correct.

When you go to nanometer channel lengths, the behavior becomes even more complicated due to short channel effects and many other effects due to diminished physical sizes.

I suggest you to run a simulation for your MOSFET to obtain the ID-VDS curve and check for the output conductance for your aimed DC operation point (Note: The small signal output conductance is also available from DC operation point information). Once you get the value, you can assign a lambda if you want (specific to that device, for that DC operating point) to be able to estimate the AC behavior by using simple models.

By the way... If you use short channel devices, be informed that the classical ID-VGS relationships will also be different (So, hand calculation may not give close results). Plus, matching may not be good if you need matched devices.

Best regards...