Question

The voltage gain of an amplifier with $9\%$ negative feedback is $10$. The voltage gain without feedback will be:

• A. $100$
• B. $90$
• C. $1.25$
• D. $10$

Answer 1

The correct option is A

$100$

Step 1: Given data

Voltage gain with negative feedback ${A_1}^{}=10$

feedback factor, $\beta =\frac{9}{100}=0.09$

Step 2: Calculation of voltage gain without feedback

The voltage gain of an amplifier with negative feedback is given by, $A_1=\frac{A}{1+\beta A}$ ,where $A$ is the voltage gain without feedback

$10=\frac{A}{1+0.09A}$

On simplifying, we get, $A(1-0.9)=10$

$A=\frac{10}{0.1}=100$

Hence, option (A) is the correct answer.