In a properly biased transistor-

Options

A. Both depletion layers are equally large
B. Both depletion layers are equally small
C. Emitter base depletion layer is large but base collector depletion layer is small
D. Emitter base depletion layer is small but base collector depletion layer is large

Answer

To solve the question regarding the behavior of a properly biased transistor, we can follow these steps:

### Step-by-Step Solution

1. **Identify the Transistor Configuration**:
- Recognize that the question pertains to a bipolar junction transistor (BJT), which has three regions: emitter, base, and collector.

2. **Understand Biasing Conditions**:
- In a properly biased transistor, the emitter-base junction is forward-biased, and the base-collector junction is reverse-biased.

3. **Draw the Diagram**:
- Sketch a simple diagram of the transistor showing the emitter, base, and collector. Indicate the forward bias on the emitter-base junction and the reverse bias on the base-collector junction.

4. **Analyze the Depletion Layers**:
- In a forward-biased junction (emitter-base), the depletion layer is small because the majority carriers are pushed into the junction.
- In a reverse-biased junction (base-collector), the depletion layer is large because the majority carriers are pulled away from the junction, widening the depletion region.

5. **Evaluate the Options**:
- Option 1: Both depletion layers are equally large. (Incorrect)
- Option 2: Both depletion layers are equally small. (Incorrect)
- Option 3: Emitter-base depletion layer is large but base-collector depletion layer is small. (Incorrect)
- Option 4: Emitter-base depletion layer is small but base-collector depletion layer is large. (Correct)

6. **Conclusion**:
- The correct answer is Option 4: "Emitter-base depletion layer is small but base-collector depletion layer is large."