I-V characteristics of four devices are shown in figure.

Identify devices that can be used for modulation

Options

A. (i) and (iii)
B. Only (iii)
C. (ii) and some regions of (iv)
D. All the devices can be used

Answer

C

Explanation

The device which follows square law is used for modulation purpose. Characteristics shown by (i) and (iii) corresponds to linear devices.
Characteristics shown by (ii) corresponds to square law device. Some part of (i) also follow square law. Hence, (ii) and (iv) can be used for modulation.