Question

In an n-p-n transistor circuit, the collector current is 10 mA. If 90% of the electrons emitted reach the collector:

• A. The base current will be 1 mA
• B. The base current will be -1 mA
• C. The emitter current will be 9 mA
• D. The emitter current will be 15 mA

Answer 1

The correct option is A

The base current will be 1 mA

Step1: Given data

Collector current, $I_c=10mA$

$I_c=90\%of{I}_e[where{I}_e=emittercurrent]$

Step2: Formula used

$I_b=I_e-I_c[where{I}_b=basecurrent,I_e=emittercurrent,I_c=collectorcurrent]$

Step3: Calculating the emitter's current

According to the question,

$$\begin{gathered} I_c=90\%of{I}_e \\ 10=\frac{90}{100}\times I_e \\ {I}_e=\frac{100}{90}\times 10 \\ {I}_e=11mA \end{gathered}$$

Step4: Calculating the base current

$$\begin{gathered} I_b=I_e-I_c \\ {I}_b=11-10 \\ {I}_b=1mA \end{gathered}$$

As a result, if $90\%$ of the released electrons reach the collector, the base current will be $1mA$.

Hence, option A is the correct answer.