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Unformatted text preview: Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Chapter12 Operational Amplifier Applications Microelectronic Circuit Design Richard C. Jaeger Travis N. Blalock Chap 12  1 Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Chapter Goals • Continue study of methods to determine transfer functions of circuits containing op amps. • Study nonideal op amp behavior. • Demonstrate circuit analysis techniques for ideal and non ideal op amps. • Learns factors involved in circuit design using op amps. • Understand frequency response limitations of op amp circuits. • Model amplifier limitations due to limited bandwidth and slew rate of the op amp. • Perform SPICE simulation of nonideal op amp circuits. Chapter Goals Chap 12  2 Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Nonideal Operational Amplifier • Various error terms arise in practical operational amplifiers due to non ideal behavior. • Some of the nonideal characteristics include: – Finite openloop gain that causes gain error – Nonzero output resistance – Finite input resistance – Finite CMRR – Commonmode input resistance – DC error sources – Output voltage and current limits Chap 113 Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Finite Openloop Gain 2 1 1 o v o v 2 1 1 1 v R R R R R R + = = + = β β is called feedback factor. β β A A v A A A A + = = − = − = = 1 s v o v ) o v s v ( ) 1 v s v ( id v o v A β is called loop gain. For A β >>1, 1 2 1 1 R R ideal A + = = β β β β β A A A + = + − = − = − = 1 s v s v 1 s v o v s v 1 v s v id v No longer zero , v id is small for large A β . Chap 114 Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Gain Error • Gain Error is given by GE= (ideal gain)(actual gain) For noninverting amplifier, • Gain error is also expressed as a fractional or percentage error. ) 1 ( 1 1 1 β β β β A A A GE + = + − = β β β β β A A A A FGE 1 1 1 1 1 1 ≅ + = + − = Chap 115 Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Gain Error: Example • Problem : Find ideal and actual gain and gain error is percent • Given data : Closedloop gain of 200 (46 dB), openloop gain of op amp is 10,000 (80 dB). • Approach :Amplifier is designed to give ideal gain and deviations from ideal case are determined. Hence, . R 1 and R 2 aren’t designed to compensate for finite openloop gain of amplifier. • Analysis : 200 1 = β 02 . 200 196 200 FGE 196 200 4 10 1 4 10 1 = − = = + = + = β A A v A Chap 116 Jaeger/Blalock 7/1/07 Microelectronic Circuit Design, 3E McGrawHill Nonzero Output Resistance Output terminal is driven by test source v x and current i x is calculated to determine output resistance (all independent sources are turned off).The equivalent circuit is same For both inverting and noninverting amplifiers....
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This note was uploaded on 07/31/2010 for the course ECE 204 taught by Professor Blalock during the Spring '09 term at UVA.
 Spring '09
 Blalock
 Amplifier, Operational Amplifier

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