Common emitter amplifier

Common emitter amplifier with RE

AC Analysis:

All capacitors are short circuited and DC source are deactivated.

Voltage gain: 

                       Av = Vo/Vin

                             = -gmx r𝝿(Rc||RL||ro)/[r𝝿+(1+gmr𝝿)RE]

Current gain 

                    Av = -gmr𝝿  = -𝜷
Input resistance 

RiB =  r𝝿+(1+gmr𝝿)RE

Ri =RTH||RiB

RiB  is input resistance looking into base of BJT

Ri is input resistance  of amplifier 

Ris is input resistance looking from source 

Output resistance:

Ro   =    Rc||RiB