In a transistor, the emitter , base and collector are respectively

Options

A. heavily doped , lightly doped , moderately doped
B. heavily doped , moderately doped , lightly doped
C. lightly doped , moderately doped, heavily doped
D. none

Answer

To solve the question regarding the doping levels of the emitter, base, and collector in a transistor, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Components of a Transistor**:
- A transistor consists of three main parts: the emitter, base, and collector.
- There are two types of transistors: NPN and PNP. Both types have these three components.

2. **Identify the Doping Levels**:
- Doping refers to the intentional introduction of impurities into a semiconductor to change its electrical properties.
- The level of doping in each part of the transistor affects its function.

3. **Doping Levels in Transistors**:
- **Emitter**: The emitter is heavily doped. This high level of doping increases the number of charge carriers (electrons or holes), allowing it to inject charge carriers into the base efficiently.
- **Base**: The base is lightly doped. This is crucial because a thin and lightly doped base allows for better control of the current flow from the emitter to the collector.
- **Collector**: The collector is moderately doped. This level of doping is sufficient to collect the charge carriers from the base without overwhelming the base's ability to control the current.

4. **Summarize the Doping Levels**:
- Emitter: Heavily doped
- Base: Lightly doped
- Collector: Moderately doped

5. **Conclusion**:
- The correct answer to the question is that the emitter is heavily doped, the base is lightly doped, and the collector is moderately doped.

### Final Answer:
- Emitter: Heavily doped
- Base: Lightly doped
- Collector: Moderately doped