In transistor, forward bias is always smaller than the reverse bias. The correct reason is

Options

A. To avoid excessive heating of transistor
B. To maintain a constant base current
C. To produce large voltage gain
D. None of these

Explanation

To understand why the forward bias in a transistor is always smaller than the reverse bias, let's break down the explanation step by step.

### Step-by-Step Solution:

1. **Understanding Transistor Structure**:
- A transistor, specifically an NPN transistor, consists of three regions: the emitter (N-type), the base (P-type), and the collector (N-type). There are two junctions: the emitter-base junction and the collector-base junction.

2. **Biasing the Transistor**:
- In a transistor, we apply biasing to control the flow of current. The emitter-base junction is forward-biased, while the collector-base junction is reverse-biased.
- Forward biasing means connecting the positive terminal of the battery to the P-type base and the negative terminal to the N-type emitter. This reduces the barrier for charge carriers (electrons and holes) to flow.

3. **Forward Bias Voltage**:
- The forward bias voltage is typically small (e.g., around 0.7 volts for silicon transistors). This small voltage allows the majority carriers to overcome the potential barrier and flow from the emitter to the base.

4. **Reverse Bias Voltage**:
- The reverse bias voltage applied to the collector-base junction is significantly larger (e.g., 15 volts). This high voltage widens the depletion region and prevents current from flowing from the collector to the base under normal conditions.

5. **Reason for Smaller Forward Bias**:
- The forward bias is kept smaller to prevent excessive heating of the transistor. If the forward bias were too high, it would lead to an increase in current, which could cause the transistor to heat up excessively and potentially damage it.

6. **Conclusion**:
- Therefore, the forward bias is always smaller than the reverse bias to ensure efficient operation of the transistor while minimizing heating effects.

### Summary:
In summary, the forward bias is smaller than the reverse bias in a transistor to avoid excessive heating, allowing for stable operation of the device.