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Common-Collector Amplifier. Section 13.1-13.4. 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.
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Common-Collector Amplifier Section 13.1-13.4
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
Vin, m=1 mV Vin,pp=2 mV Vout,pp=1.47 mV Av(ADS)=0.735 Av(matlab)=0.783
Large Signal Behavior of Common-Collector Amplifier The output does not track the input during the negative swing.
Vin, m=1.71 V VBE
Push-Pull Stage Q1 pushes current into RL. Q1 and Q2 are off. Q1 pulls current from RL.
Vout Versus Vin Crossover Distortion
Improved Push-Pull Stage Q1 and Q2 can not be on at the same time! V1=Vout+VBE1 V2=Vout-|VBE2| Keep Q1 and Q2 on V1-V2=VBE1+|VBE2|=VB
Implementation of VB Add I1 to provide current For D1 and D2.
Output Stage with no DC shift If I1=I2 and IB1 and IB2, the input source does not sink or source Output voltage.