The dc current gain of a transistor in CB configuration is 0.99 . Find its dc current gain in CE configuration.

Options

A. 99
B. 400
C. 300
D. 50

Answer

To find the DC current gain in the common emitter (CE) configuration given the DC current gain in the common base (CB) configuration, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given values:**
- The DC current gain in the common base configuration (α) is given as 0.99.

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

3. **Substitute the known value of α into the formula:**
- Plugging in the value of α:
\[ \beta = \frac{0.99}{1 - 0.99} \]

4. **Calculate the denominator:**
- Calculate \(1 - 0.99\):
\[ 1 - 0.99 = 0.01 \]

5. **Perform the division:**
- Now substitute this value back into the equation for β:
\[ \beta = \frac{0.99}{0.01} \]

6. **Calculate β:**
- Performing the division gives:
\[ \beta = 99 \]

7. **Conclusion:**
- The DC current gain in the common emitter configuration (β) is 99.

### Final Answer:
The DC current gain in the common emitter configuration is **99**.

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