15.7 Graphically illustrate the effect of the Rs and RD resistances on the ID-VD

Question

15.7 Graphically illustrate the effect of the Rs and RD resistances on the ID-VD character- istics. Referring to Exercise 15.3, write a MATLAB (computer) program that can be used to calculate and plot the J-FET ID-VD characteristics for arbitrary values of Rs and RD. Nor- FIELDEFFECT INTRODUCTION-THEJFETAND MESFET 5 malize all ID values to I 1Dsativa o as computed from Eq. (15.13). (The normalized current relationships should involve only ID/IDO or IDsat/IDo, VD, VG, and the parameters Vti, VP, GORs, and GORD, where G 2azunNDaIL) un your program, assuming Vbi 1 V and V 2.5 V; successively set GOR GAR 0, 0.1, and 0.5. Compare your S results with Fig. 15.16. Comment on the comparison.

Explanation / Answer

clear all;

%kn=un*cox = 100 microA/Volts

kn=1e-4;

%Let W/L= 2

W=360*(10^(-9));

L=180*(10^(-9));

beta=kn*W/L;

%Vth is the threshold voltage

Vth=1;

%Sweep drain to source voltge from 0 to 10V

vds=0:0.5:10;

%Ask the user to enter gate to source voltage

vgs=input('ENTER THE Vgs in volts');

%Estimate length of the array

m=length(vds);

for i=1:m

if vgs < Vth

current(1,i)=0;

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

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

elseif vds(i) < (vgs - Vth)

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

end

end

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

xlabel('Vds, V')

ylabel('Drain Current,A')

title('I-V Characteristics of a MOSFET')

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