I wanted to use a BSIM4 model of NMOS in my circuit. I got the correct dc biasing point, certain VDS,VGS and IC. But I am having issues measuring S-parameter data for MOSFET amplifiers. I simulated circuits in BJT and it works fine. Is there any generic circuit for MOSFET? I am not sure where to put up the DC block and RF feed with proper biasing in MOSFET (NMOS)so that S-parameter data could be measured. I ended up with the circuit shown below, it has invalid data for S-paramters if measured. Any suggestion/correction in the circuitry will be very much helpful.
I am getting the S21 (dB) is below, which is invalid:
My bias points are VDS=0.5V, VGS=0.8V, IDS=45.48uA and supply VDD=1.2V. Hence I got RDS(which is R1)=15.39kohms.