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Differential and MultistageAmplifiers

Outline

•The MOS Differential Pair•Small-Signal Operation of the MOS Differential Pair•The BJT Differential Pair•Other Nonideal Characteristics of the Differential

Amplifier•The Differential Amplifier with Active Load•Frequency Response of the Differential Amplifier•Multistage Amplifiers

Differential-to-Single-Ended

A Simple but inefficient approach Active-Loaded

Active-Loaded Differential Pair

Circuit at equilibrium Differential input applied

Short-Circuit Transconductance Gm

Differential Gain = Short-circuit transconductance Gm Output resistance Ro

Output Resistance Ro

Differential Gain = Short-circuit transconductance Gm Output resistance Ro

Ad =

Common-Mode Gain and CMRR

BJT Differential Pair with Active Load

Gm =Rid =

Ro and Ad

Ro = Ad =

Common-Mode Gain and CMRR

Systematic Input Offset Voltage

VOS =

Higher Voltage Gain with Active Load

Ad =

Outline

•The MOS Differential Pair•Small-Signal Operation of the MOS Differential Pair•The BJT Differential Pair•Other Nonideal Characteristics of the Differential

Amplifier•The Differential Amplifier with Active Load•Frequency Response of the Differential Amplifier•Multistage Amplifiers

Resistively Loaded MOS Amplifier

Differential Half-Circuit

Acm and fZ

Common-mode Half-circuit

CM Gain, Diff Gain, and CMRR