In which of the configuration of a transistor , the power gain is highest ?

Options

A. Common base
B. Common emitter
C. Common collector
D. Same in all the three

Answer

To determine which configuration of a transistor provides the highest power gain, we can analyze the three common configurations: Common Base, Common Emitter, and Common Collector.

### Step-by-Step Solution:

1. **Understand the Transistor Configurations**:
- **Common Base (CB)**: The base terminal is common to both input and output. It has low input impedance and high output impedance.
- **Common Emitter (CE)**: The emitter terminal is common to both input and output. It has high input impedance and moderate output impedance.
- **Common Collector (CC)**: The collector terminal is common to both input and output. It has high input impedance and low output impedance.

2. **Analyze Input and Output Impedance**:
- The **Common Emitter configuration** has a high input impedance and a lower output impedance compared to the Common Base configuration. This allows for better voltage transfer and higher power gain.

3. **Evaluate Voltage and Power Gain**:
- The **Common Emitter configuration** is known for providing high voltage gain. Since power gain is a product of voltage gain and current gain, the high voltage gain in the Common Emitter configuration translates to high power gain as well.

4. **Comparison with Other Configurations**:
- The **Common Base configuration** typically has low voltage gain and, consequently, low power gain.
- The **Common Collector configuration** (also known as an emitter follower) provides good current gain but has a voltage gain of approximately 1, resulting in lower power gain compared to the Common Emitter.

5. **Conclusion**:
- Based on the analysis, the **Common Emitter configuration** provides the highest power gain among the three configurations.

### Final Answer:
The configuration of a transistor in which the power gain is highest is the **Common Emitter configuration**.