When the emitter current of a transistor is changed by 1 mA, its collector current changes by 0.990 mA. In the common base circuit, current gain for the transistor is

Options

A. 0.099
B. 1.01
C. 1.001
D. 0.99

Answer

To find the current gain (α) of a transistor in a common base configuration, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Given Information**:
- The change in emitter current (ΔIe) is given as 1 mA.
- The change in collector current (ΔIc) is given as 0.990 mA.

2. **Recall the Formula for Current Gain (α)**:
- In a common base configuration, the current gain (α) is defined as:
\[ \alpha = \frac{\Delta I_c}{\Delta I_e} \]

3. **Substitute the Given Values into the Formula**:
- Substitute ΔIc = 0.990 mA and ΔIe = 1 mA into the formula:
\[ \alpha = \frac{0.990 \, \text{mA}}{1 \, \text{mA}} \]

4. **Calculate the Current Gain**:
- Since both values are in mA, we can simplify:
\[ \alpha = 0.990 \]

5. **Final Result**:
- The current gain (α) of the transistor in the common base circuit is:
\[ \alpha = 0.99 \]

6. **Identify the Correct Option**:
- Among the given options, the correct answer is option 4, which is 0.99.