Question

5. In common base connection, current amplification factor is 0.9, if emitter current is 1mA, find the base current​

Answer 1

Given:

The current amplification factor is 0.9

i.e. α= 0.9

The emitter current is 1mA

i.e. $\displaystyle I_{e}$ = 1mA

To find:

The base current​ = $\displaystyle I_{b}$ ?

Explanation:

We have to find a current gain

$\displaystyle \beta = \frac{\alpha }{1 -\alpha }$

     =    $\displaystyle\frac{0.9}{1-0.9}$

  β = 9

Now we have to find a collector current

$\displaystyle I_{e}$  = α× $\displaystyle I_{c}$

1    = 0.9 × $\displaystyle I_{c}$

$\displaystyle \mathbf { I_{c}}$ =  1.11 mA

Now we have to calculate a base current

$\displaystyle I_{b } = \frac{I _c}{\beta }$

    = $\displaystyle \frac{1.11}{9}$

β = 1.12 mA

Answer 2

Answer:

GIVEN:

alpha = 0.9mA

Ie = 1mA

TO FIND:

Ib = ?

SOLUTION:

$\beta = \alpha \div 1 - \alpha$

$\beta = 0.9 \div (1 - 0.9) \\ \\ \alpha = ic \div ib \\ \\ ic = \alpha ib \\ ic = 0.9 \times 1 = 0.9 \\ ie = ic + ib \\ ib \: = ie - ic \\ ib = 1 - 0.9 = 0.1$

Ib = 0.1 mA