How Do You Calculate Diode Parameters from Characteristic Points?

[elbw]

Hi

Please help me to solve the following problem:

Homework Statement

There are three points given on diode characteristic (1N4148 diode)

Q1=(50uA, 0.6V)
Q2=(500uA, 0.7V)
Q3=(2mA, 0.75V)

I have to calculate:

Is - reverse bias saturation current
n - emission coefficient

Homework Equations

I suppose I have to use Shockley equation
$$I_F = I_S ( e^\frac{U_F}{nU_T} - 1)$$

The Attempt at a Solution

UT = 20mV

but solving for Is and n seems to be very complicated


$$n=\frac{U_F}{ln(\frac{I_F}{I_S} +1) U_T }$$

$$I_S=\frac{I_F}{e^\frac{U_F}{nU_T}-1}$$

Are above equations correct?

 

[Valkarie]

How do I solve it? Yes, the equations are correct. To solve the problem you will need to use the values of Q1, Q2, and Q3 to determine the values of I_F, U_F, and I_S. Using these values, you can then calculate n by plugging them into the equation for n. Once you have calculated n you can then calculate I_S using the equation for I_S.