How do I figure out the (x, y) values of where two lines intersect on a graph?

Below I have code that plots two equations and I am trying to figure out how to find the (x,y) values of where the two equations intersect on this graph.

code

x = 0:.1:9;

q=1.6022e-19

C=28.73

T=273+C

k=1.3806e-23

Is=1.0e-12

V= 0:0.01:9

n=1

Vt=(k*T)/q

Id=Is*((exp(V/(n*Vt)))-1)

plot(V,Id)

axis([-1,0.6,-0.1,2])

grid on

title('V-T Characteristics of Diode')

xlabel(' Voltage ')

ylabel(' Current ')

hold on

I = (-1/5000)*x + .0018;

plot(x,I)

Answer 1

[Star Strider]

First, ‘x’ and ‘V’ have to have the same numbers of elements (unless you’re defining them as functions, in which case you can use fzero or fsolve to determine the intersection).

With that constraint, this works:

x = linspace(0, 9);
q=1.6022e-19;
C=28.73;            
T=273+C        
k=1.3806e-23;  
Is=1.0e-12;      
V= x;  
n=1;       
Vt=(k*T)/q;
Id=Is*((exp(V/(n*Vt)))-1);
loglog(V,Id)
axis([-1,0.6,-0.1,2])
grid on
title('V-T Characteristics of Diode')
xlabel(' Voltage ')
ylabel(' Current ')
 
hold on
I = (-1/5000)*x + .0018;
plot(x,I)

xint = interp1(Id-I, x, 0);
yint = (-1/5000)*xint + .0018;
plot(xint, yint, 'pg')

producing:

xint =
   0.546332230872042

yint =
   0.001690733553826

[Nathan Donatell]

Thank you

[Star Strider]

My pleasure!

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