Question

For circuit shown below Vin = 3V, R1 = 6K, R2 = 2K. The voltage V will be ________ (Use constant voltage drop model assumption and take VD = 0.5V)

(a) 2V

(b) 3V

(c) 3.5V

(d) 2.5V

I got this question during an internship interview.

The doubt is from Constant Voltage Drop Model-2 in portion Diode Circuit of Analog Circuits

Answer 1

The correct choice is (d) 2.5V

The explanation is: 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 and parallel to resistor R1 voltage drop across diode is VD. So net voltage equals to Vin – VD.