Question

A change of 8.0 mA in the emitter current brings a change of 7.9mA in the collector current. How much change in the base current is required to have the same change 7.9 mA in the collector current? Find the values of alpha and beta .

Answer 1

Change in the base current is required to have the same change 7.9 mA in the collector current is

Explanation:

Given :

Change in emitter current $\Delta I _{E} = 8$ mA

Change in collector current $\Delta I _{C} = 7.9$ mA

From the fundamental theorem transistor,

  $\Delta I_{E} = \Delta I _{B} + \Delta I _{C}$

So for change in base current,

 $\Delta I_{E} - \Delta I _{C} = \Delta I _{B}$

 $\Delta I_{B} = 8 - 7.9$

 $\Delta I_{B} = 0.1$ mA

For find the value of $\alpha$,

Current gain in case of CB configuration = $\frac{\Delta I_{C} }{\Delta I_{E} }$

      $\alpha = \frac{7.9}{8}$

      $\alpha = 0.99$

Current gain in case of CE configuration = $\frac{\Delta I_{C} }{\Delta I_{B} }$

      $\beta = \frac{7.9}{0.1}$

      $\beta = 79$

Therefore, the value of $\alpha = 0.99$ and $\beta = 79$