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

Options

A. (a)200
B. (b)99
C. (c)199
D. (d)None of these

Answer

To find the current gain in the common emitter mode (β) given the current gain in the common base mode (α), we can use the relationship between these two gains.

### Step-by-Step Solution:

1. **Understand the Relationship**:
The relationship between the current gain in common base mode (α) and the current gain in common emitter mode (β) is given by the formula:
\[ \beta = \frac{\alpha}{1 - \alpha} \]

2. **Substitute the Given Value**:
We are given that α = 0.995. We can substitute this value into the formula:
\[ \beta = \frac{0.995}{1 - 0.995} \]

3. **Calculate the Denominator**:
Now, calculate the denominator:
\[ 1 - 0.995 = 0.005 \]

4. **Complete the Calculation**:
Substitute the value of the denominator back into the equation for β:
\[ \beta = \frac{0.995}{0.005} \]

5. **Perform the Division**:
Now, perform the division:
\[ \beta = 199 \]

6. **Conclusion**:
Therefore, the current gain in the common emitter mode is:
\[ \beta = 199 \]

### Final Answer:
The gain in the common emitter mode is 199.

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