In n-p-n transistor circuit, the collector current is 20 mA. If `90%` of the electrons emitted reache the collector, then the

Options

A. Emitter currect will be about 16 mA
B. Emitter current will be 19 mA
C. Base current will be about 2 mA
D. Base current will be about 10 mA

Answer

To solve the problem, we need to find the emitter current (I_E) and the base current (I_B) in an n-p-n transistor circuit where the collector current (I_C) is given as 20 mA and 90% of the electrons emitted reach the collector.

### Step-by-Step Solution:

1. **Understanding the Given Information**:
- Collector Current (I_C) = 20 mA
- Percentage of electrons reaching the collector = 90%

2. **Finding the Emitter Current (I_E)**:
- Since 90% of the emitted electrons reach the collector, this means that the collector current is 90% of the emitter current.
- Mathematically, this can be expressed as:
\[ I_C = 0.9 \cdot I_E \]
- Rearranging the equation to find I_E:
\[ I_E = \frac{I_C}{0.9} = \frac{20 \, \text{mA}}{0.9} \]
- Calculating I_E:
\[ I_E = \frac{20}{0.9} = 22.22 \, \text{mA} \]

3. **Finding the Base Current (I_B)**:
- We know that the relationship between the emitter current, collector current, and base current is given by:
\[ I_E = I_C + I_B \]
- Rearranging this for I_B:
\[ I_B = I_E - I_C \]
- Substituting the values we found:
\[ I_B = 22.22 \, \text{mA} - 20 \, \text{mA} = 2.22 \, \text{mA} \]

### Final Results:
- Emitter Current (I_E) = 22.22 mA
- Base Current (I_B) = 2.22 mA