# Single Transistor Overall Current Gain

1. May 28, 2013

### hisotaso

1. The problem statement, all variables and given/known data
THe problem statement and given solutions are in this thread:

I do not understand the equation for current gain:

2. Relevant equations
Ai = $\alpha$$\frac{R4}{R4 + Ri}$

3. The attempt at a solution
I have pages of work on this, but basically what I know is $\frac{Io}{Ie}$ = $\alpha$

then $\frac{Ie}{Ii}$ must equal $\frac{R4}{R4 + Ri}$, I don't see that.

2. May 28, 2013