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

Explanation

To solve the problem 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 Roles of Each Region**:
- The **emitter** is responsible for injecting charge carriers (electrons or holes) into the base.
- The **base** is a thin region that allows the majority of the charge carriers to pass through to the collector.
- The **collector** collects the charge carriers from the base.

2. **Identify the Doping Levels**:
- The **base** has the **lowest doping level** because it needs to be lightly doped to allow charge carriers to pass through easily.
- The **collector** has a **moderate doping level**. It needs to be more heavily doped than the base to effectively collect the charge carriers.
- The **emitter** has the **highest doping level** since it must inject a large number of charge carriers into the base.

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

### Final Arrangement:
- The order of increasing doping levels is: **Base < Collector < Emitter**.

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