Invalid expression. Check for missing multiplication operator, missing or

clear all
close all
clc
 
%Constants 
q=l.6e-19;
k=8.625e-5;
e0=8.854e-14;

%Device, Material, and System Parameters
ni=l.5e10; 
esi=ll.8; 
T=300;
a=l.5e-4; 
z=50e-4; 
L=5e-4; 
ND=2el5;
VG=[0 -.5 -1 -1.5 -2];
%Contact Potential
V0=.55+k*T*log(ND/ni);
%mobility calculation
NDref=1.3el7; 
mu_n_min=92; 
mu_n_0=1268; 
alpha_n=0.91;
mun=mu_n_min+mu_n_0./(1+(ND/NDref).^alpha_n)
%Resistivity 
sigma=q*ND*mun; 
rho=l/sigma;
%Mutual Transconductance 
G0=2*a*z/(rho*L)
%Pinch—off voltage 
VP=V0-q*a^2*ND/(2*e0*esi)
% Calculate ID as a function of VD 
VD=linspace(0,abs(VP)+5,100);
for j=1:1:length(VG) 
for i=1:1:length(VD)
    if VD(i)<(VG(j)-VP)	%Linear regime
        ID(j,i)=G0*(VD(i)-2/3*(V0-VP)*(((VD(i)+V0-VG(j))/(V0-VP)).^(3/2)-((V0-VG(j))/(V0-VP)).^(3/2)));
    else
        VD(i)=VG(j)-VP;	
        ID(j,i)=G0*(VD(i)-2/3*(V0-VP)*(1-((V0-VG(j))/(V0-VP)).^(3/2)));
    end
end
end
VD=linspace(0,abs(VP)+5,100);	%Voltage vector re—generation for plotting
plot(VD,ID*le6)
hold on
xlabel ('VD (Volts)')
ylabel ('ID (Microampere) ') 
title('JFET I—V Characteristics') 
grid
%Code ends

Answer 1

[Image Analyst]

It doesn't like your decimal point. What is it? If I copy and paste your number into the command window, it complains about the decimal point but if I type it in myself directly, it works fine. Maybe you used some sort of higher order unicode decimal point.

[Filip Vucak]

Got it, thank you!

Answer 2

[Walter Roberson]

q=l.6e-19;

The decimal point is fine, but that is a lower-case L, not a one, before the decimal point.