2011-07-01 Finding the potential and current in a diode circuit.

Find V_X and the current flowing in the Si diode.

Solution

Since the potential +20 V is higher than 0V, the Ge and Si diodes tend to be forward biased.

KVL;

+20 V - 0.3 V - 0.7 V = V_x

V_x = 19 V Ans

KVL;

0 V + (1 kΩ)(I_1kΩ) = V_x = 19 V

I_1kΩ = 19 mA

KVL;

V_x + 0.7 V = V_x + (2 kΩ)(I_2kΩ)

I_2kΩ = 0.7 V / 2 kΩ = 0.35 mA

KCL;

I_Si + I_2kΩ = I_1kΩ

(6 kΩ)(I_4kΩ) = 9.7 V

I_Si = 19 mA - 0.35 mA = 18.65 mA Ans