Power AmplifiersClass B, AB,C(CMOS 0.35um,0.18um)

Imran Khan

Contents

Introduction

Class AB,B,C

Results

Conclusion

Power Amplifiers

Introduction BFL (choke inductor) has a large

value in order to provide an approx. constant current.

Vdd is fixed for every technology Vin is the input voltage to be amplified

Linearity Ideal PA is linear but other

PAs are linear in certain limits

Efficiency Normally 30% to 80% Efficiency=Pout/Pin

Power Amplifiers

IntroductionGain (voltage, current, power gain)

magnitude of the output signal (Xo) over the magnitude of the input signal (Xi), G= Xo/Xi

Region of Operation The region of operation of MOSFET is:

Power Amplifiers Amplifier Classes

Class A Efficiency: (10-20)%, theory 50%

Linearity: good, Cond. Cycle: 360º

Class B Efficiency: (35-50)%, theory 78 %

Linearity: <A, Cond. Cycle: 180º

Class AB Efficiency: compromise between A& B

Linearity: between A and B, Cond. Cycle: 181º-359º

Class C Efficiency: (50-60)% max 90% Linearity:

worst, Cond. Cycle:<180

Current FlowingThe red indicates how much of the drain current is flowing through one wave cycle.

Results- Class B (0.18um)

W=375um

Vlow=0.39 V

Results- Class B (0.18um)

Results- Class AB (0.18um)

W=90um

Vlow=0.35um

Results- Class AB (0.18um)

Results- Class C (0.18um)

W=950um

Vlow=0.1V

Results- Class C (0.18um)

Results- Class B (0.35um)

W=1250um

Vlow=0.1V

Results- Class B (0.35um)

W=350um

Vlow=0.6V

Results- Class AB (0.35um)

Results- Class AB (0.35um)

Results- Class C (0.35um)

W=2.5mm

Vlow=0V

Results- Class C (0.35um)

Conclusion

Except class A, all PA can be used in Rf systems

PA is the last element in transmission chain therefore requires most attention.