The current gain in transistor in common base mode is 0.99. To change the emitter current by 5 mA, the necessary change in collector will be

Options

A. 0.196 mA
B. 2.45 mA
C. 4.95 mA
D. 5.1 mA

Explanation

To solve the problem, we need to use the relationship between the emitter current (\(I_E\)), collector current (\(I_C\)), and the current gain (\(\alpha\)) in a common base configuration of a transistor.

### Step-by-Step Solution:

1. **Understand the relationship**: In a common base configuration, the current gain (\(\alpha\)) is defined as:
\[ \alpha = \frac{\Delta I_C}{\Delta I_E} \]
where \(\Delta I_C\) is the change in collector current and \(\Delta I_E\) is the change in emitter current.

2. **Given values**: From the problem, we know:
- \(\alpha = 0.99\)
- \(\Delta I_E = 5 \, \text{mA}\)

3. **Rearranging the formula**: We need to find \(\Delta I_C\). Rearranging the formula gives:
\[ \Delta I_C = \alpha \cdot \Delta I_E \]

4. **Substituting the known values**: Now, substitute the known values into the equation:
\[ \Delta I_C = 0.99 \cdot 5 \, \text{mA} \]

5. **Calculating \(\Delta I_C\)**:
\[ \Delta I_C = 4.95 \, \text{mA} \]

6. **Final answer**: Therefore, the necessary change in collector current is:
\[ \Delta I_C = 4.95 \, \text{mA} \]

### Summary:
The necessary change in collector current when the emitter current changes by 5 mA with a current gain of 0.99 is **4.95 mA**.

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