For a common emitter transistor as amplifier current gain is 72.Calculate the base current for which emitter current is 8.9 milliampere and also find collector current.

Explanation

`beta=72, I_(e)= 8.9mA= 8.9 xx 10^(-3)A, I_(b)= ? I_(c)= ?`
`beta= (I_(c))/(I_(b)) 72= (I_(c))/(I_(b))`
`rArr I_(c)= 72 I_(b)`
But `I_(e) = I_(b) + I_(c)`
`8.9 = I_(b) + I_(b) + 72 I_(b)= 73 I_(b)`
`I_(b)= (8.9)/(73) = 0.122mA`
`rArr I_(c)= 72I_(b) = 72 xx 0.122`
`I_(c)= 8.78mA`