Hello,
What is the method of finding Resistance out and Resistance in for any of the BJT variations? Thanks

 

There are two different resistances to be considered for transistors and generally active devices, the DC resistance and the AC or incremental resistance. The DC resistance equals the DC voltage divided by the DC current. The AC resistance is a different concept and it depends on the bias point of the transistor. Generally, the impedance looking into the base of the transistor equals

Zb=25mV/Ib

and the impedance looking into the emitter of the transistor is

Ze=25mV/Ie

where

Ib=DC bias current through the base
Ie-DC bias current through the emitter