Common-Base Amplifier

Common-Base Amplifier

Response of CB Stage to small Input Change

Input Impedance

Application of CB Stages

Response to a Source of Finite Source Resistance

Output Impedance

Input Impedance

General CB

(VA=infinity, RB>0)

Base resistance (RB) decreases voltage gain.

CB Stage with Biasing

Design Goal

Goal: i2>>i1

Bypass Capacitor

(Base resistance decreases gain!)

Design Guideline

• Given: Rin, AV• Select RE>>(1/gm). – gm →IC.– RE=10Rin

• Av=gmRC →RC

• Vb=IERE+VBE• Let I(R1)=40IB →(R1+R2) • R2 is known from Vb and R1.• 1/(C1ω)=(1/gm)/20• 1/(beta+1)/(C1 ω)=(1/gm)/20

Common Base Amplifier

ADS SimulationADS Analysi

s

Vs,pp(mV) 4 4

Vin,pp(mV) 2 1.90

Vout,pp(mV) 17 N/A

Vout,pp/Vin,pp 8.5 11

Vout,pp/Vs,pp 4.25

5.23