Common-Collector Amplifier Section 5.3

Topics Emitter Follower Core Effect of Transistor Output Resistance Emitter Follower with Biasing

Voltage Gain of Emitter Follower

Use a current source to implement RE RE=infinity imples that AV=1

Thinking of an Emitter follower as a voltage divider

Source Resistance Included

Input Resistance

Output Resistance RS is transformed to a smaller output resistance.

Application of Common Collector Stage Av=-(RC||Rsp)/(1/gm) RSP=8 Ohms << RC AV=-RSP/(1/gm)

Interpose a Emitter Follower between the CE Stage and the speaker CE stage: -(RC||Rin1)/(1/gm)

Inclusion of Output Resistance

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

Common-Collector Amplifier

Vin,pp=2 mV Vout,pp=1.47 mV Av(ADS)=0.735 Av(matlab)=0.783

Vin, m=1.71 V Need to adjust V_RE.