115A_1_EE115A_W10-Chap8

115A_1_EE115A_W10-Chap8 - Chapter 8 Operational Amplifier...

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Chapter 8 Operational Amplifier as A Black Box h 8.1 General Considerations h 8.2 Op-Amp-Based Circuits 351 h 8.3 Nonlinear Functions h 8.4 Op-Amp Nonidealities h 8.5 Design Examples
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Chapter Outline CH8 Operational Amplifier as A Black Box 352
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Basic Op Amp CH8 Operational Amplifier as A Black Box 353 h Op amp is a circuit that has two inputs and one output. h It amplifies the difference between the two inputs. ( ) 2 1 0 in in out V V A V - =
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Inverting and Non-inverting Op Amp CH8 Operational Amplifier as A Black Box 354 h If the negative input is grounded, the gain is positive. h If the positive input is grounded, the gain is negative.
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Ideal Op Amp h Infinite gain h Infinite input impedance CH8 Operational Amplifier as A Black Box 355 h Zero output impedance h Infinite speed
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Virtual Short CH8 Operational Amplifier as A Black Box 356 h Due to infinite gain of op amp, the circuit forces V in2 to be close to V in1 , thus creating a virtual short.
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Unity Gain Amplifier 0 ) ( V V A V out in out - = CH8 Operational Amplifier as A Black Box 357 0 0 1 A A V V in out + =
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Op Amp with Supply Rails CH8 Operational Amplifier as A Black Box 358 h To explicitly show the supply voltages, V CC and V EE are shown. h In some cases, V EE is zero.
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Noninverting Amplifier (Infinite A 0 ) 1 1 R V out + = CH8 Operational Amplifier as A Black Box 359 h A noninverting amplifier returns a fraction of output signal thru a resistor divider to the negative input. h With a high A o , V out /V in depends only on ratio of resistors, which is very precise. 2 R V in
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Noninverting Amplifier (Finite A 0 ) CH8 Operational Amplifier as A Black Box 360 h The error term indicates the larger the closed-loop gain, the less accurate the circuit becomes. + - + 0 2 1 2 1 1 1 1 1 A R R R R V V in out
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Extreme Cases of R 2 (Infinite A 0 ) CH8 Operational Amplifier as A Black Box 361 h If R 2 is zero, the loop is open and V out /V in is equal to the intrinsic gain of the op amp. h If R 2 is infinite, the circuit becomes a unity-gain amplifier and V out /V in becomes equal to one.
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Inverting Amplifier CH8 Operational Amplifier as A Black Box 362 h Infinite A 0 forces the negative input to be a virtual ground. 2 1 2 1 0 R R V V R V R V in out in out - = = -
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Another View of Inverting Amplifier CH8 Operational Amplifier as A Black Box 363 Inverting Noninverting
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0 CH8 Operational Amplifier as A Black Box 364 h The larger the closed loop gain, the more inaccurate the circuit is. + -
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This note was uploaded on 01/08/2011 for the course EE 115 taught by Professor Kaiser during the Spring '09 term at UCLA.

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115A_1_EE115A_W10-Chap8 - Chapter 8 Operational Amplifier...

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