Diodes and their applications

Explanation of question 8

A varactor diode is normally operated

1. forward-biased, and as a variable inductor
2. forward-biased, and as a variable capacitor
3. reverse-biased, and as a variable inductor
4. reverse-biased, and as a variable capacitor

The answer is :- 4 The varactor (varicap) diode behaves as a variable capacitor. It is normally operated in the reverse-biased mode. As such, a change in applied p.d. will give a small change in capacitance. If forward-biased, the change in capacitance would be large.