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//first we define all parameters for the transistor and the circuit
Z0=50; //characteristic imedance of the system
Vcc=3.6; //power supply voltage
Vce=2; //collector voltage
Ic=10e-3; //collector current
T=300; //ambient temperature (300K)
//transistor parameters (they are very similar to BFG403W)
beta=145; // current gain
Is=5.5e-18; // saturation current
VAN= 30; // forward Early voltage
tau_f=4e-12; // forward transition time
rb=125; // base resistance
rc=15; // collector resistance
re=1.5; // emitter resistance
Lb=1.1e-9; // base inductance
Lc=1.1e-9; // collector inductance
Le=0.5e-9; // emitter inductance
Cjc=16e-15; // collector junction capacitance at zero applied voltage
mc=0.2; // collector junction grading coefficient
Cje=37e-15; // emitter junction capacitance at zero applied voltage
me=0.35; // emitter junction grading coefficient
phi_be=0.9; // base-emitter diffusion potential
phi_bc=0.6; // base-collector diffusion potential
Vbe=phi_be; // base-emitter voltage
// some physical constants
k=1.38e-23; // Boltzmann's constant
q=1.6e-19; // elementary charge
VT=k*T/q; // thermal potential
disp('DC biasing parameters');
Ib=Ic/beta;
disp("Amperes",Ib,"Base current");
Rc=(Vcc-Vce)/Ic;
disp("Ohms",Rc,"Collector resistance");
Rb=(Vcc-Vbe)/Ib;
disp("Ohms",Rb,"Base resistance");
r_pi=VT/Ib;
disp("Ohms",r_pi,"Rpi");
r0=VAN/Ic;
disp("Ohms",r0,"R0");
gm=beta/r_pi;
disp("Mho",gm,"Gm");
Vbc=Vbe-Vce;
Cmu=Cjc*(1-Vbc/phi_bc)^(-mc);
disp("Farads",Cmu,"base collector capacitance");
if(Vbe<0.5*phi_be)
Cpi_junct=Cje*(1-Vbe/phi_be)^(-me);
else
C_middle=Cje*0.5^(-me);
k_middle=1-0.5*me;
Cpi_junct=C_middle*(k_middle+me*Vbe/phi_be);
end;
disp("Farads",Cpi_junct,"Junction Capacitance");
Cpi_diff=Is*tau_f/VT*exp(Vbe/VT);
disp("Farads",Cpi_diff,"Differential capacitance");
Cpi=Cpi_junct+Cpi_diff;
disp("Farads",Cpi,"Total Capacitance");
C_miller=Cmu*(1+gm*r_pi/(r_pi+rb)*Z0*r0/(r0+rc+Z0));
disp("Farads",C_miller,"Miller Capacitance");
C_input=Cpi+C_miller;
disp("Farads",C_input,"Total input capacitance");
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