%% Progrma to calculte the gain and input resistance of a common-gate
%% amplifier. Executing this program requires Symbolic Analysis toolbox.
%% The program makes use of node analysis.
clear all
clc
syms gm ro gmb Rs Rd Vin

M=[1/ro+1/Rd,-gm-gmb-1/ro;-1/ro,gm+gmb+1/ro+1/Rs];  % Matrix
N=[0;1/Rs];                                        % Vector

X=inv(M)*N;

fprintf('Amplifier Gain: \n')
Gain=simplify(X(1));
pretty(Gain)

Gin=simplify((1-X(2))/Rs);
Rin=1/Gin;
Rin=subs(Rin,Rs,0);
fprintf('Input Resistance: \n')
pretty(Rin)