Question

A transistor has a voltage gain \( A \). If the amount \( \beta A \) of its output is applied to the input of the transistor, then the transistor becomes oscillator when

• A. \( \beta = 0 \)
• B. \( \beta A = 1 \)
• C. \( \beta A = \infty \)
• D. \( \beta A = 0 \)

Hint:

In oscillators, the feedback factor and voltage gain must satisfy the condition \( \beta A = 1 \) for sustained oscillations.

Answer 1

The Correct Option is B

Step 1: Oscillator condition.
For a transistor to become an oscillator, the feedback must be such that the total gain around the loop is equal to one. This occurs when the product of the feedback factor \( \beta \) and the voltage gain \( A \) is equal to one.
Step 2: Conclusion.
The condition for the transistor to oscillate is \( \beta A = 1 \), so the correct answer is (B).