What is the definition of FT and how to simulate it ?

[flushrat]

how to simulate ft cmos

What is the definition of ft?
And how to simulate it with hspice?

 

[ezt]

ft for cmos

Hi.
The following formula is from the 2nd chapter of Razavi's book, Analog CMOS IC Design. But note that this formula isn't correct for submicron devices :

ft=gm/2pi(Cgd+Cgs) = µn/2pi * (Vgs-Vth)/L^2

and in HSpice, I think you can use a test circuit. you should use a small-signal current source for example with 1V ac and use an AC analysis to find the frequency where the current gain of the device drops to unity.

Regards,
EZT

 

[flushrat]

Re: about ft of cmos device

Thanks very much.
According your method, I simulated a nmos of .18 process.
Attatch is ft~vgs, vds=1.2v