A transistor has a voltage gain 'A'. If the amount ' β A^′ of its output is appl put of the transistor, then the transistor becomes oscillator where

Correct answer: (B) β A=1. The voltage gain of oscillator circuit is given by A_f=A/(1-A β) where, A is the voltage gain without feedback and p is called feedback factor. For sustained oscillation, from Barkhausen criterion A β=1

Q116 / 150 · MHT CET 2020 (16 Oct Shift 2) · Physics

A transistor has a voltage gain 'A'. If the amount ' $\beta A^{\prime}$ of its output is appl put of the transistor, then the transistor becomes oscillator where

A
$\beta=0$
Correct answer
B
$\beta \mathrm{A}=1$
C
$\beta A=\infty$
D
$\beta A=0$

Solution

The voltage gain of oscillator circuit is given by $A_{f}=\frac{A}{1-A \beta}$ where, $\mathrm{A}$ is the voltage gain without feedback and $\mathrm{p}$ is called feedback factor. For sustained oscillation, from Barkhausen criterion $A \beta=1$

Hence, the correct answer is option: 'B'.

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