Topics Emitter Follower as a power amplifier Push and Pull Output Stage
Design Guideline Specs: Av, rsp, v_re gm=Av/(1-Av)/rsp Calculate IC from gm. Determine re from IC and V_RE Calculate VBE. Calculate VB. Calculate IB from IC. Assume that I1=40 IB Calculate R2 from VB. Calcualte R1
Voltage Gain from Vin to VN Full circuit To compute VN/Vin, Calculate RN and multiply RN by gm4.
Voltage Gain from N to Out Full circuitGeneral formula: RL/(1/gm+RL)
Small Signal Model of BJT Transistors (NPN)(PNP)
Sanity Check Intuition: gm1=gm2, rpi1=rpi2 Vout/VN=(1+2gm rpi/2)/(rpi/2/RL+1+2gm rpi/2) =(1+beta)/(rpi/2/RL+1+beta) ~=1/(rpi/2/RL/beta+1) =RL/(/(2gm)+RL) Compare Vout /Vn to the generic formula: RL/(1/gm+RL) we see that this formula makes sense!