The current gain for transistor working as a common base amplifier is 0.96.If the emitter current is 7.2mA, then the base current is

Options

A. 0.29mA
B. 0.35mA
C. 0.39mA
D. 0.43mA

Answer

To find the base current (IB) of a transistor working as a common base amplifier, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Given Values**:
- Current gain (α) = 0.96
- Emitter current (IE) = 7.2 mA

2. **Use the Relationship for Current Gain**:
- The relationship for current gain in a common base amplifier is given by:
\[ \alpha = \frac{\Delta I_C}{\Delta I_E} \]
- Where:
- \( \Delta I_C \) = Collector current
- \( \Delta I_E \) = Emitter current

3. **Calculate Collector Current (IC)**:
- Rearranging the formula gives:
\[ \Delta I_C = \alpha \times \Delta I_E \]
- Substituting the known values:
\[ \Delta I_C = 0.96 \times 7.2 \, \text{mA} \]
- Performing the multiplication:
\[ \Delta I_C = 6.912 \, \text{mA} \approx 6.91 \, \text{mA} \]

4. **Use the Relationship Between Emitter, Collector, and Base Currents**:
- The relationship is given by:
\[ I_E = I_C + I_B \]
- Rearranging this gives:
\[ I_B = I_E - I_C \]

5. **Calculate Base Current (IB)**:
- Substituting the values we have:
\[ I_B = 7.2 \, \text{mA} - 6.91 \, \text{mA} \]
- Performing the subtraction:
\[ I_B = 0.29 \, \text{mA} \]

6. **Final Answer**:
- The base current (IB) is **0.29 mA**.