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Amin Arbabian Jan M. Rabaey

Lecture 3: Transistors, Amplifiers and Bandwidth Limitations

EE142 – Fall 2010 Introduction

Sept. 2nd, 2010

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At a glance

  Previous lecture: modulation   Today: transistors, amplifiers

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Amplifiers in Transceivers

  Used in many functions …   Key requirement: bandwidth

– What limits the bandwidth?

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CMOS Cross Section

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Small Signal Model

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Simplified Small Signal Model

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MOS Device Characteristics

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Transconductance

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Unity Gain Frequency

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MOS Unity Gain Frequency

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Modern Bipolar Device

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Bipolar “Gain”

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Small Signal Model

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Generic Small Signal Model (High Freq.)

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Bipolar Unity Gain Frequency

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Bias Dependence

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Single Stage Amplifiers

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Basic Amplifiers and their Small Signal Modles

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A Broadband Amplifier: Current Amplifier

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Current Amplifier Analysis

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CS/CE Bandwidth Limitation

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CS/CE Gain-Bandwidth Product

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Example

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Common Base Amplifier

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Common Base Amplifier (2)

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Common Base Bandwidth

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Matched Common Base Amplifier

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Shunt Feedback Amplifier

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Gain and Input Resistance

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Shunt Feedback Amplifier BW

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Shunt Feedback/Common Collector Cascade

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Wideband Two Stage Amplifiers