Question

A transistor has a voltage gain A. If the amount βA of its output is applied to the input of the transistor, then the transistor becomes oscillator, when ______.

Options

• βA = 0

• βA = 1

• βA = ∞

• β = 0

Answer 1

A transistor has a voltage gain A. If the amount βA of its output is applied to the input of the transistor, then the transistor becomes oscillator, when βA = 1.

Explanation:

The voltage gain of oscillator circuit is given by

`"A"_"f" = "A"/(1 - "A"beta)`

where, A is the voltage gain without feedback and p is called feedback factor.

For sustained oscillation, from Barkhausen criterion

Aβ = 1