Question

In common emitter mode of a transistor, the current gain is 8. The input impedance is 25kΩ and load resistance is 75kΩ. The power gain is

• A. 192
• B. 112
• C. 316
• D. 224

Hint:

The power gain of a common emitter amplifier is the product of the current gain squared and the ratio of load to input resistance.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Power gain \(=\) voltage gain \(\times\) current gain, and voltage gain \(= \beta \dfrac{R_L}{R_i}\). So power gain \(= \beta^2 \dfrac{R_L}{R_i}\).

Step 2: Calculation
\(\beta = 8\), \(R_L = 75\ \text{k}\Omega\), \(R_i = 25\ \text{k}\Omega\). Then \(\dfrac{R_L}{R_i} = 3\).

Step 3: Power Gain
Power gain \(= 8^2 \times 3 = 64 \times 3 = 192\).

Step 4: Compare the options
The power gain is 192, the first option.

Final Answer:
The power gain is 192. \[ \boxed{\text{(A) }192} \]