EE 435 Lect 2 Spring 2010

EE 435 Lect 2 Spring 2010 - EE 435 Lecture 2: Basic Op Amp...

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1 EE 435 Lecture 2: Basic Op Amp Design - Single Stage Low Gain Op Amps
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2 How does an amplifier differ from an operational amplifier? Review from last lecture: ? Operational Amplifier used in feedback applications Amplifier used in open-loop applications Op Amp Amplifier
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3 Conventional Wisdom Does Not Always Provide Correct Perspective – Review from last lecture: even in some of the most basic or fundamental areas !! Just because its published doesn’t mean its correct Just because famous people convey information as fact doesn’t mean they are right Keep an open mind about everything that is done and always ask whether approach others are following is leading you in the right direction
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4 What is an Operational Amplifier? Textbook Definition: Voltage Amplifier with Very Large Gain Very High Input Impedance Very Low Output Impedance Differential Input and Single-Ended Output Review from last lecture:
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5 What is an Operational Amplifier? Amplifier with Very Large Gain Review from last lecture:
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6 Are differential input and single- ended outputs needed? Consider Basic Amplifiers Inverting Amplifier Noninverting Amplifier Only single-ended input is needed for Inverting Amplifier ! Many applications only need single-ended inputs ! Review from last lecture:
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7 Basic Inverting Amplifier Using Single-Ended Op Amp Inverting Amplifier with Single-Ended Op Amp Review from last lecture:
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8 Fully Differential Amplifier Widely (almost exclusively) used in integrated amplif Seldom available in catalog parts 2 2 1 1 IN OUT Review from last lecture:
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9 What is an Operational Amplifier? Conventional Wisdom does not provide good guidance on what an amplifier or an operational amplifier should be! Lets see what the experts say ! What are the implications of this observation?
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10 Basic Op Amp Design Outline Fundamental Amplifier Design Issues Single-Stage Low Gain Op Amps Single-Stage High Gain Op Amps Two-Stage Op Amp Other Basic Gain Enhancement Approaches
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11 Single-Stage Low-Gain Op Amps Single-ended input Differential Input (Symbol not intended to distinguish between different amplifier types)
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12 Single-ended Op Amp Inverting Amplifier V OUT V IN V YQ V XQ Slope = -A ( ) IN OUT V f V = Consider: Assume Q-point at {V XQ ,V YQ } () ( ) OUT IN xQ YQ VA V V V =− + When operating near the Q-point, the linear and nonlinear model of the amplifier are nearly the same If the gain of the amplifier is large, V XQ is a characteristic of the amplifier
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13 Single-ended Op Amp Inverting Amplifier ( )( ) O1 X Q Y Q 12 1O I N V = - A V - V + V RR V = V + V R+R () 00 I N X Q Y Q -A V+ V -V +V ⎛⎞ ⎜⎟ ⎝⎠ 1 11 2 0i S S I N Q X Q Y Q 1 1 2 R -A A V +V V V R A1 + A A R + R + ++ If we define V iSS by V IN =V INQ +V iSS V OUT V IN V YQ V XQ Slope = -A Eliminating V 1 we obtain:
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14 Single-ended Op Amp Inverting Amplifier () 22 Oi n s s X Q X Q i n Q 11 RR V = - V + V + V -V 1 2 12 0i S S I N Q X Q Y Q 1 R -A A V = V + V V V R A1 + A A R + R ⎛⎞⎛
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This note was uploaded on 01/31/2012 for the course EE 345 taught by Professor Geiger during the Fall '11 term at Iowa State.

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EE 435 Lect 2 Spring 2010 - EE 435 Lecture 2: Basic Op Amp...

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