Question

The current gain of a common emitter amplifier is $69$. If the emitter current is $7.0mA$, collector current is:
A.) $9.6mA$
B.) $6.9mA$
C.) $0.69mA$
D.) $69mA$

Answer 1

Hint: In this use the relationship of the collector current , base current and emitter current i.e. ${i_E} = {i_B} + {i_{_C}}$, ${i_B}$is a small amplifier applications and current gain (ratio of output current ${i_C}$ to input current ${i_B}$) is large.

Complete step-by-step answer:

Formula Used: ${i_E} = {i_B} + {i_{_C}}$, ${i_B}$is a small amplifier applications and current gain (ratio of output current ${i_C}$ to input current ${i_B}$) is large.
According to the question , $69$ is the current gain of a common emitter amplifier

Hence , Current gain of CE amplifier $ = \beta $

$
  {i_c} = \beta {i_b} = \alpha {i_e} \\
  \alpha = \dfrac{\beta }{{\beta + 1}} \\
  {i_c} = \dfrac{\beta }{{\beta + 1}}{i_e} \\
  {i_c} = \dfrac{{69}}{{70}} \times 7 \times {10^{ - 3}}A \\
  {i_c} = 6.9mA \\
$

Note: Emitter is a part of a moderately sized and heavily doped transistor on one side (to increase the current). It offers a wide range of charging carriers for the rest. Base is the thin size central section, which is doped lightly (to minimize recombination). Collector is the largest size at one end of the transistor, and is moderately doped. It collects a majority of majority charge carriers.