Calculate the output impedance of the emitter-follower circuit called the pass transistor: assume that beta=200

**see attached diagram**

I don't know how to do this, I thought that it would just be the 1k resistor, because that is the resistor that we are measuring vout across, but I don't think that is it.... any help would be great!!

 

If memory serves correct, I believe the formula you are looking for is Zin = Beta * Emitter Resistor (200 * 1k)

 

The question actually relates to the output resistance rather than input resistance.

 

Rout is approximately Re|| (re+Rbase/β)

re=26/Ie(mA)

Assume a β of say 200.

Rbase= 6k8||10k

Re=1K

Then you have it.