Question

In the circuit below Vin = 4V, R = 2K and VB = 2V. In these conditions the voltage across diode V is _________ (Use constant voltage drop model assumption and take VD = 0.5V)

(a) 2.5

(b) 4.5

(c) 0.5

(d) 1.5

The question was posed to me during an internship interview.

Origin of the question is Constant Voltage Drop Model-2 topic in portion Diode Circuit of Analog Circuits

Answer 1

Right option is (c) 0.5

For explanation: In constant voltage drop model at forward bias diode can be replaced as a cell and in reverse bias diode can be avoided by considering the terminals are open. Since diode is forward biased it will produce a voltage drop of VD.