Which of the following break down of pn junction is reverisble?

Options

A. Avalanche breakdown
B. Zener breakdown
C. Dielectric breakdown
D. All of these

Answer

To determine which breakdown of a pn junction is reversible, we will analyze the different types of breakdown mechanisms associated with pn junctions.

### Step-by-Step Solution:

1. **Identify the Types of Breakdown**:
- The common types of breakdown in pn junctions are Avalanche Breakdown, Zener Breakdown, and Dielectric Breakdown.

2. **Avalanche Breakdown**:
- In Avalanche Breakdown, carriers (electrons) are generated due to collisions with lattice atoms caused by a high reverse-bias voltage. This process leads to a multiplication of charge carriers and can cause thermal damage to the diode.
- **Conclusion**: This breakdown is not reversible because it can permanently damage the diode.

3. **Zener Breakdown**:
- Zener Breakdown occurs in heavily doped pn junctions where a strong electric field at the junction breaks covalent bonds, generating carriers. This process is characterized by a low breakdown voltage and does not involve significant thermal dissipation.
- **Conclusion**: Zener Breakdown is reversible because after the breakdown, the diode can return to its original state and can be used again without damage.

4. **Dielectric Breakdown**:
- Dielectric Breakdown refers to the failure of insulating materials to prevent current flow under high voltage. Once breakdown occurs, the insulating properties are compromised.
- **Conclusion**: This breakdown is also not reversible, as the material may no longer function as an insulator.

5. **Final Decision**:
- Based on the analysis, the only reversible breakdown mechanism among the options provided is the **Zener Breakdown**.

### Answer:
The breakdown of a pn junction that is reversible is **Zener Breakdown**.

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