Question

In a common base connection, current amplification factor is 0.9. If the

emitter current is 1mA, determine the value of base current.

Answer 1

Ib = 0.1 mA

Step-by-step explanation:

You want the base current in a common-base circuit that has an emitter current of 1 mA and an amplification factor of 0.9.

Setup

The amplification factor (gain) is the ratio of collector current to emitter current. The emitter current is the sum of the collector current and the base current. Thus, we have two equations that let us solve for the base current:

Ib +Ic = Ie

Ic/Ie = gain

Solution

Solving the second equation for Ic gives ...

Ic = Ie·gain

Substituting into the first equation, we have ...

Ib +Ib·gain = Ie

And solving for Ib gives ...

Ib = Ie(1 -gain) = (1 mA)(1 - 0.9) = 0.1 mA

The value of the base current is 0.1 mA.