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Lect2UP190_(100327)

# Lect2UP190_(100327) - Lecture 190 Differential Amplifier...

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Lecture 190 – Differential Amplifier (3/27/10) Page 190-1 CMOS Analog Circuit Design © P.E. Allen - 2010 LECTURE 190 – DIFFERENTIAL AMPLIFIER LECTURE ORGANIZATION Outline • Characterization of a differential amplifier • Differential amplifier with a current mirror load • Differential amplifier with MOS diode loads • An intuitive method of small signal analysis • Large signal performance of differential amplifiers • Differential amplifiers with current source loads • Design of differential amplifiers • Summary CMOS Analog Circuit Design, 2 nd Edition Reference Pages 180-199 Lecture 190 – Differential Amplifier (3/27/10) Page 190-2 CMOS Analog Circuit Design © P.E. Allen - 2010 CHARACTERIZATION OF A DIFFERENTIAL AMPLIFIER What is a Differential Amplifier? A differential amplifier is an amplifier that amplifies the difference between two voltages and rejects the average or common mode value of the two voltages. Differential and common mode voltages: v 1 and v 2 are called single-ended voltages. They are voltages referenced to ac ground. The differential-mode input voltage, v ID , is the voltage difference between v 1 and v 2 . The common-mode input voltage, v IC , is the average value of v 1 and v 2 . ± v ID = v 1 - v 2 and v IC = v 1 + v 2 2 ² v 1 = v IC + 0.5 v ID and v 2 = v IC - 0.5 v ID v OUT = A VD v ID ± A VC v IC = A VD ( v 1 - v 2 ) ± A VC ³ ´ ´ µ · · ¸ v 1 + v 2 2 where A VD = differential-mode voltage gain A VC = common-mode voltage gain + - + v OUT - v IC v ID 2 v ID 2 Fig. 5.2-1B

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