Question

The current gain of a transistor in a common base arrangement is $0.98$. Find the changes in collector current corresponding to a change of $5.0$ mA in emitter current. What would be the change in base current?

• A. $4.9mA,0.1mA$
• B. $4.9mA,0.2mA$
• C. $5.9mA,0.3mA$
• D. $5.9mA,0.8mA$

Answer 1

Answer: (A)

$4.9mA,0.1mA$

Given:

Current gain of a transistor, $\alpha =0.98$

Change in the emitter current, $\Delta i_e=5.0\text{mA}$

The current gain of a transistor ($\alpha$) is the ratio of collector current ($\Delta i_c$) to the emitter current ($\Delta i_e$) of a transistor

$\Rightarrow \alpha =\frac{\Delta i_c}{\Delta i_e}$

Substituting the given values,

$\Rightarrow 0.98=\frac{\Delta i_c}{5.0}$

$\Rightarrow \Delta i_c=0.98\times 5.0=4.9\text{mA}$

The change in collector current is 4.9 mA

The change in base current can be found by the formula

$\Delta i_b=\Delta i_e-\Delta i_c$

Substituting the values,

$\Rightarrow \Delta i_b=5.0-4.9=0.1\text{mA}$

The change in base current is 0.1 mA

Therefore, Option (A) will be the right answer.