Question

If resistance R1 is 10K, V2 = 2V, V1 = 3V then the current I through the circuit will be ___________ (Use constant voltage drop model of diode and take VD as 0.5V)

(a) 0.3mA

(b) 0.6mA

(c) 0.7mA

(d) 0.1mA

I got this question in my homework.

Question is taken from Constant Voltage Drop Model-1 topic in portion Diode Circuit of Analog Circuits

Answer 1

The correct answer is (d) 0.1mA

For explanation: In ideal diode model the diode is considered as a perfect conductor in forward bias and perfect insulator in reverse bias. That is voltage drop at forward bias is zero and current through the diode at reverse bias is zero.

Since both voltage is reverse bias to diode the diode will disappear from the circuit. Then effective voltage becomes 3-2 = 1V so current is 1/10K = 0.1mA.