The heavily and lightly doped regions of a bipolar junction transistor are respectively

Options

A. base and emitter
B. base and collector
C. emitter and base
D. collector and emitter

Explanation

To answer the question regarding the heavily and lightly doped regions of a bipolar junction transistor (BJT), we can break down the information step by step.

### Step-by-Step Solution:

1. **Understanding Bipolar Junction Transistor (BJT)**:
- A BJT consists of three regions: the emitter, the base, and the collector. There are two types of BJTs: PNP and NPN.

2. **Doping Levels**:
- Doping refers to the introduction of impurities into a semiconductor to change its electrical properties. The level of doping can be classified as heavily doped, moderately doped, or lightly doped.

3. **Emitter Region**:
- The emitter is the region that injects charge carriers into the base. In a BJT, the emitter is heavily doped. This heavy doping ensures that a large number of charge carriers (either holes in PNP or electrons in NPN) are available for injection into the base region.

4. **Base Region**:
- The base is the region that receives the charge carriers from the emitter. The base is lightly doped to allow for efficient injection of carriers from the emitter while also ensuring that the carriers can recombine effectively. This light doping helps maintain a small base current.

5. **Collector Region**:
- The collector is the region that collects the charge carriers from the base. The collector is usually moderately doped, which allows it to collect the carriers without causing excessive recombination.

6. **Conclusion**:
- Therefore, in a bipolar junction transistor, the heavily doped region is the emitter, and the lightly doped region is the base.

### Final Answer:
- The heavily doped region of a bipolar junction transistor is the **emitter**, and the lightly doped region is the **base**.

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