Which of the following is true?

Options

A. common base transistor is commonly used bacause current gain is maximum.
B. common-emitter is commonly used because current gain is maximum.
C. Common collector is commonly used because current gain is maximum.
D. Common emitter is the least used transistor.

Answer

To determine which statement is true regarding the common base, common emitter, and common collector configurations of transistors, we can analyze each configuration step by step.

### Step 1: Understanding the Configurations
1. **Common Emitter (CE)**: This configuration is widely used in amplifiers. It provides a good balance of voltage gain, current gain, and power gain.
2. **Common Base (CB)**: This configuration is less commonly used. It has low input impedance and high output impedance, and it provides a current gain of less than 1.
3. **Common Collector (CC)**: Also known as an emitter follower, this configuration has high input impedance and low output impedance. It provides a current gain greater than 1 but does not provide voltage gain.

### Step 2: Analyzing Power Gain
- The **power gain** in a common emitter configuration is maximum compared to the other two configurations. This is one of the reasons why it is widely used in amplification applications.

### Step 3: Current and Voltage Gain
- In the common emitter configuration:
- **Current Gain (β)**: It is typically greater than 1, meaning the output current is amplified.
- **Voltage Gain (Av)**: It can also be greater than 1, but it is not as high as the power gain.
- The output signal is inverted (180 degrees out of phase) with respect to the input signal.

### Step 4: Impedance Levels
- The common emitter configuration provides medium input and output impedance levels, making it suitable for various applications.

### Conclusion
Based on the analysis:
- The common emitter configuration is the most widely used due to its maximum power gain and significant current gain. Therefore, the correct statement is that the **common emitter configuration has maximum current gain**.

### Final Answer
The correct answer is **Common Emitter** is commonly used because **current gain is maximum**.

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