%% Define Constants
Vt=0.5;
un=350;   %cm^2/Vs
W=300;    %nm
L=150;    %nm
ti=50e-7; %cm
Vds=0:0.01:3;
%% Calculate Ci
ei=3.9;
e0=8.854e-14;  %F/cm
Ci=ei*e0/ti;   %F/cm^2
%% Vgs=0V
Vgs=1;
Vds_sat = Vgs-Vt;

p(x)=piecewise(x < Vds_sat,un*Ci*W/L*((Vgs-Vt).*Vds - 0.5.*(Vds.^2)), 0.5*un*Ci*W/L*(Vgs-Vt)^2);

plot(Vds, p(Vds))