Question

The input voltage V1 of the circuit the circuit is 2V and resistor has a resistance of 1KΩ. The cut-in voltage of the silicon diode is 0.7V and the reverse saturation current is 10^-8A. The temperature at which diode operates is 30°C. The voltage across resistor when diode starts conducting is _________________

(a) 0.7V

(b) 1.3V

(c) 0.306V

(d) 1.7V

This question was addressed to me by my school principal while I was bunking the class.

This interesting question is from Characteristic Equation of Diode-2 topic in chapter Diode Circuit of Analog Circuits

Answer 1

Right option is (b) 1.3V

To explain: V1 = IR1 + VD

For silicon diode, cut-in voltage is 0.7V.

Hence IR1 = 2-0.7 = 1.3V

Drop across the resistor is 1.3V.