A transistor has three impurity regions , emitter , base and collector. Arrange them in order of increasing doping levels.

Options

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

Answer

To solve the question of arranging the impurity regions of a transistor (emitter, base, and collector) in order of increasing doping levels, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Function of Each Region**:
- The **emitter** is responsible for injecting charge carriers (electrons or holes) into the base. It needs to be highly doped to ensure a large number of charge carriers are available for injection.
- The **base** is the region where the charge carriers recombine. It is intentionally kept lightly doped to allow for efficient control of the charge carriers flowing from the emitter to the collector.
- The **collector** collects the charge carriers that have traversed the base. It is moderately doped, more than the base but less than the emitter.

2. **Identify Doping Levels**:
- **Emitter**: Highly doped (highest concentration of impurities).
- **Collector**: Moderately doped (intermediate concentration of impurities).
- **Base**: Lightly doped (lowest concentration of impurities).

3. **Arrange in Order of Increasing Doping Levels**:
- Based on the doping levels identified, we can arrange them as follows:
- Base (least doped)
- Collector (moderately doped)
- Emitter (most doped)

4. **Final Arrangement**:
- Therefore, the order of increasing doping levels is: **Base < Collector < Emitter**.

### Conclusion:
The correct arrangement of the transistor regions in order of increasing doping levels is:
**Base, Collector, Emitter**.