EE142 Lecture26

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Amin ArbabianJan M. Rabaey

Lecture 26:VCOsIntroduction to PAs

EE142 – Fall 2010

Dec. 2nd, 2010

University of California, Berkeley

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Review

One-Port, negative resistance view of oscillators discussed as another method to analyze/design oscillators.

Differential oscillators. Today:

– Voltage (/Current) Controlled Oscillators (VCOs)

– Introduction to Power Amplifiers Challenges Efficiency/Output Power/Class-A Operation/…

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Virtual Ground

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Voltage-Controlled Oscillators

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PN Junction Varactors

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Doping Profile

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Varactor-Tuned LC Oscillator

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Clapp VCO

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Varactor-Tuned Differential Oscillator

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Varactor-Tuned Differential Oscillator (2)

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MOS Varactors

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MOS Varactors (2)

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Accumulation Mode MOS Varactors (A-MOS)

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Switched Capacitor Varactors

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APPENDIXCRYSTAL OSCILLATORS

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Crystal Oscillators

The piezoelectric crystal is an electro-mechanical device with a sharp frequency selective response.

Equivalent Q > 10,000 are available. The piezoelectric material exhibits a transduction

between mechanical strain and electric charge. Very good stability and low temperature coefficient.

Example:f=1.59 MHz (series)R = 125 Ω, L = 250 mH, C = 40 fF, Co = 4 pF

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Crystal Oscillators

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POWER AMPLIFIERS:AN INTRODUCTION

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Power Amplifiers

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Audio PA

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PA Efficiency

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Cell-Phone PA

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High Voltage/ Current

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Effect of Loss

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PA Design Considerations

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Emitter Follower

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Normalized Voltage/ Current Swing

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Current Swing

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Voltage Swing

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Voltage Swing (2)

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Follower Efficiency

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Common-Emitter (Common-Source) PA

The CE amplifier has the advantage of higher power gain (there is voltage gain and current gain). The collector efficiency is given by

As before, the efficiency is maximized if we can set the voltage swing and current swing independently.

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Voltage Swing

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Current Swing

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Optimum Load

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Inductor Loading

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Inductor Voltage

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Collector Efficiency

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“Complete” PA

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Package Parasitics

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Emitter Degeneration

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Advanced Packaging