# The script sets up the bias voltage and fruency sweep
# and calculates the input impedance of the MOSFET

load('nmos_ac.ldev');

switchtolayout;

setnamed('CHARGE','log start frequency',1e6);
setnamed('CHARGE','log stop frequency',2e10);
setnamed('CHARGE','num frequency points per dec',3);

select("CHARGE::boundary conditions::gate");
set('bc mode','steady state');
set('sweep type','range');
set('range start',0);
set('range stop',2);
set('range interval',0.2);
set('apply ac small signal','last');

select("CHARGE::boundary conditions::drain");
set('bc mode','steady state');
set('sweep type','single');
set('voltage',5);
set('apply ac small signal','none');

run;

ac_data = getresult('CHARGE','ac_gate');
Iac = pinch(ac_data.dI);
f = ac_data.f;
Vac = ac_data.dV_gate;
Zin = Vac/Iac;
plot(f*1e-9,abs(Zin),'Freq (GHz)','|Zin| (Ohm)','','log10x,log10y');
plot(f*1e-9,angle(Zin)*180/pi,'Freq (GHz)','angle[Zin] (degree)','','log10x');

matlabsave('nmos_Zin',Zin,f);