Question

In the given circuit input voltage Vin is 3V and VB is 1V. The resistance R is 1K. Cut-in voltage of diode is 0.5V. Forward bias resistance is 10Ω. The current I will be? (Use piecewise linear model of diode)

(a) 1V

(b) 3V

(c) 2.3V

(d) 1.3V

This question was addressed to me in an interview for internship.

Question is from Piecewise Linear Model of Diode in division Diode Circuit of Analog Circuits

Answer 1

The correct choice is (b) 3V

To explain: If we consider diode as a short circuit, the voltage in circuit is thus 3-1=2V and current flows from top to bottom across diode. But that only happens in a reverse bias of the diode. Hence the diode is in reverse bias and open. Output voltage V=3V.