hope to add the graph line, It is basic please help

The below is the current result. (just 1 Vgs line)

However, i want that my graph is to be like the below. (4 Vgs lines)

My current coding is the below. what should i do just for adding the Vgs line?? (Ignore numeric values)

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clear all;

W=40;

Vth=0.45;

Leff=0.15;

k=4.255*(10^-4)*(W/Leff);

lambda=25*10^-5;

Vds=linspace(0,2.5);

vgs=0.7;

m=length(Vds);

for i=1:m

if vgs < Vth

current(1,i)=0;

elseif Vds(i) >= (vgs - Vth)

current(1,i)=0.5* k * ((vgs - Vth)^2);

elseif Vds(i) < (vgs - Vth)

current(1,i)= k*((vgs-Vth)*Vds(i) - 0.5*(Vds(i)^2));

end

end

plot(Vds,current(1,:),'b')

Answer 1

[Star Strider]

Create a vector out of the ‘vgs’ quantities you want to plot:

vgs=[0.7 1 1.5 2];

then use a second loop to index them:

W=40;
Vth=0.45;
Leff=0.15;
k=4.255*(10^-4)*(W/Leff);
lambda=25*10^-5;
Vds=linspace(0,2.5);
vgs=[0.7 1 1.5 2];
m=length(Vds);
for k1 = 1:numel(vgs)
for i=1:m
    if vgs(k1) < Vth
        current(k1,i)=0;
    elseif Vds(i) >= (vgs(k1) - Vth)
        current(k1,i)=0.5* k * ((vgs(k1) - Vth).^2);
    elseif Vds(i) < (vgs(k1) - Vth)
        current(k1,i)= k*((vgs(k1)-Vth)*Vds(i) - 0.5*(Vds(i).^2));
    end
end
end

figure
plot(Vds,current, 'LineWidth',1.5)
grid
legend(compose('V_{GS} = %0.1f V', vgs), 'Location','NW')

Add a legend call and the plot does what you want.