The current gain `alpha` of a transistor in common base mode is 0.995 . Its gain .. in the common emitter mode is

Options

A. 200
B. 99
C. 199
D. None of these

Answer

To find the current gain in the common emitter mode (denoted as β) given the current gain in the common base mode (denoted as α), we can use the relationship between α and β.

### Step-by-Step Solution:

1. **Identify the given value**:
- We have α = 0.995.

2. **Use the relationship between α and β**:
- The relationship is given by the formula:
\[ \beta = \frac{\alpha}{1 - \alpha} \]

3. **Substitute the value of α into the formula**:
- Plugging in the value of α:
\[ \beta = \frac{0.995}{1 - 0.995} \]

4. **Calculate the denominator**:
- Calculate \(1 - 0.995\):
\[ 1 - 0.995 = 0.005 \]

5. **Substitute back into the equation**:
- Now substituting the denominator back:
\[ \beta = \frac{0.995}{0.005} \]

6. **Perform the division**:
- Now, calculate the value:
\[ \beta = 199 \]

7. **Final Answer**:
- Thus, the gain in the common emitter mode is:
\[ \beta = 199 \]