The base current in a transistor is `100 mu A ` and the collector current is 3 mA . The emitter current is

Options

A. `3.9 mA`
B. `3.1 mA
C. 2.4 mA
D. 2.1 mA

Answer

To find the emitter current in a transistor given the base current and collector current, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Given Values**:
- Base current (I_B) = 100 µA
- Collector current (I_C) = 3 mA

2. **Convert Base Current to Milliampere**:
- Since the collector current is given in milliampere, we should convert the base current from microampere to milliampere.
- 1 mA = 1000 µA, therefore:
\[ I_B = 100 \, \mu A = \frac{100}{1000} \, mA = 0.1 \, mA \]

3. **Use the Emitter Current Formula**:
- The emitter current (I_E) in a transistor is given by the formula:
\[ I_E = I_B + I_C \]

4. **Substitute the Values**:
- Now substitute the values of I_B and I_C into the formula:
\[ I_E = 0.1 \, mA + 3 \, mA \]

5. **Calculate Emitter Current**:
- Adding these values gives:
\[ I_E = 3.1 \, mA \]

6. **Final Answer**:
- The emitter current is \( 3.1 \, mA \).