Question

A $n-p-n$ transistor is connected to common emitter configuration in a given amplifier. A load resistance of $800$ is connected in the collector circuit and the voltage drop across it is $0.8\, V$. If the current amplification factor is $0.96$ and the input resistance of the circuit is $192\,\Omega$, the voltage gain and the power gain of the amplifier will respectively be

• A. 3.69, 3.84
• B. 4 , 4
• C. 4, 3.69
• D. 4, 3.84

Answer 1

The Correct Option is D

Voltage and Power Gain Calculations 

Given:

\(\alpha = 0.96\)

Step 1: Calculate $\beta$:

Using the formula for $\beta$:

\(\beta = \frac{\alpha}{1 - \alpha}\)

\(\beta = \frac{0.96}{0.04}\)
\(\Rightarrow \beta = 24\)

Step 2: Calculate Voltage Gain for Common Emitter Configuration:

Using the formula for voltage gain in common emitter configuration:

\(A_V = \beta \times \frac{R_L}{R_1}\)

\(A_V = 24 \times \frac{800}{192}\)
\(\Rightarrow A_V = 100\)

Step 3: Calculate Power Gain for Common Emitter Configuration:

Using the formula for power gain:

\(P_V = \beta \times A_V\)

\(P_V = 24 \times 100\)
\(\Rightarrow P_V = 2400\)

Step 4: Calculate Voltage Gain for Common Base Configuration:

Using the formula for voltage gain in common base configuration:

\(A_V = \alpha \times \frac{R_L}{R_P}\)

\(A_V = 0.96 \times \frac{800}{192}\)
\(\Rightarrow A_V = 4\)

Step 5: Calculate Power Gain for Common Base Configuration:

Using the formula for power gain in common base configuration:

\(P_V = A_V \times \alpha\)

\(P_V = 4 \times 0.96\)
\(\Rightarrow P_V = 3.84\)

Conclusion:

The problem asks about the common emitter configuration, but we have also calculated the values for the common base configuration. Based on the above calculations, the voltage gain and power gain for the common emitter configuration are:

• \(voltage\ Gain\ for\ Common\ Emitter\: A_V = 100\)
• \(power\ Gain\ for\ Common\ Emitter\: P_V = 2400\)