How can I calculate the output impedance of an emitter follower (see the last post for details) and of a transformer? How matching impedances helps us increasing power transfer? Help!

Question

anonymous · Answer

the input impedance: The impedance when you are looking from the input of a device to know the value of the all load from this point " the input"
and viceversa for the output impedance
which is the one when you are looking from the output " here the emitter"

For the follower emitter :
$$Rin =RB+Beta*(Hib+RL//RE)$$       where RB= R1// R2  bias resistors

$$Rout=[RE//hib]+RB divBeta$$

nick67 · Answer

@emicho
uhm... I'm not sure about Rout formula; could you better explain how did you obtain it ?

anonymous · Answer

|dw:1342867918740:dw|

well if we look at the equivalence circuit and if we include the source resistor"for more details" 

we will see That Ro is equal to  Re//( hib + (Rs//Rb)/Beta )..
that's as i guess :)