What is the unit of current gain of a transistor?

Options

A. No unit
B. ampere
C. Volt
D. ohm

Answer

To determine the unit of current gain of a transistor, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Current Gain**: Current gain in a transistor is defined as the ratio of output current to input current. It shows how much the output current is amplified compared to the input current.

2. **Identify the Currents**: In a transistor, we typically refer to three currents:
- \( I_E \): Emitter current
- \( I_C \): Collector current
- \( I_B \): Base current

3. **Current Gain Formula**: The current gain can be expressed in different configurations:
- In Common Base (CB) configuration, the current gain \( \alpha \) is defined as:
\[ \alpha = \frac{I_C}{I_E} \]
- In Common Emitter (CE) configuration, the current gain \( \beta \) is defined as:
\[ \beta = \frac{I_C}{I_B} \]

4. **Analyze the Units**: Since current is measured in amperes (A), we can analyze the units in the current gain formulas:
- For \( \alpha \):
\[ \text{Unit of } \alpha = \frac{\text{A}}{\text{A}} = 1 \quad (\text{no unit}) \]
- For \( \beta \):
\[ \text{Unit of } \beta = \frac{\text{A}}{\text{A}} = 1 \quad (\text{no unit}) \]

5. **Conclusion**: Since both \( \alpha \) and \( \beta \) are ratios of currents, they are dimensionless quantities, meaning they do not have any units.

### Final Answer:
The unit of current gain of a transistor is **dimensionless (no unit)**.

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