Hi all,
I am trying to design an RF CMOS PA and I face the following problem:
I am biasing the PA at 0.5V using a voltage swing of 0.6V (trying for it to be class B) with a fairly large FET (W = 3200 u, L = 0.35u). When I simulate the PA, the Fet seems to never turn off and always draws DC current from the source! however when I use a smaller FET the problem ceases to exist and the PA works fine. I also see an abnormal spike in small frequences during the AC simulation when I use the large FET.
Is  this normal? I suspect it's a parasitic effect that must be faced.
The frequency of operation is 2.4GHz.
I can post the simulation results if it helps

Thanks in advance,
Giannis