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 head2right 8.1 General Considerations head2right 8.2 Op-Amp-Based Circuits 351 head2right 8.3 Nonlinear Functions head2right 8.4 Op-Amp Nonidealities head2right 8.5 Design Examples

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Chapter Outline CH8 Operational Amplifier as A Black Box 352
Basic Op Amp CH8 Operational Amplifier as A Black Box 353 head2right Op amp is a circuit that has two inputs and one output. head2right 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 head2right If the negative input is grounded, the gain is positive. head2right If the positive input is grounded, the gain is negative.
Ideal Op Amp head2right Infinite gain head2right Infinite input impedance CH8 Operational Amplifier as A Black Box 355 head2right Zero output impedance head2right Infinite speed

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Virtual Short CH8 Operational Amplifier as A Black Box 356 head2right Due to infinite gain of op amp, the circuit forces V in2 to be close to V in1 , thus creating a virtual short.
Unity Gain Amplifier 0 ) ( A V V V A V out in out = - = CH8 Operational Amplifier as A Black Box 357 0 0 1 A V in out +

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Op Amp with Supply Rails CH8 Operational Amplifier as A Black Box 358 head2right To explicitly show the supply voltages, V CC and V EE are shown. head2right In some cases, V EE is zero.
Noninverting Amplifier (Infinite A 0 ) 2 1 1 R R V V in out + = CH8 Operational Amplifier as A Black Box 359 head2right A noninverting amplifier returns a fraction of output signal thru a resistor divider to the negative input. head2right With a high A o , V out /V in depends only on ratio of resistors, which is very precise.

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Noninverting Amplifier (Finite A 0 ) CH8 Operational Amplifier as A Black Box 360 head2right 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
Extreme Cases of R 2 (Infinite A 0 ) CH8 Operational Amplifier as A Black Box 361 head2right If R 2 is zero, the loop is open and V out /V in is equal to the intrinsic gain of the op amp. head2right 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 0 V V - CH8 Operational Amplifier as A Black Box 362 head2right Infinite A 0 forces the negative input to be a virtual ground. 2 1 2 1 R R V V R R in out in out - = =
Another View of Inverting Amplifier CH8 Operational Amplifier as A Black Box 363 Inverting Noninverting

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Gain Error Due to Finite A 0 + - - 1 1 1 1 1 R R V out CH8 Operational Amplifier as A Black Box 364 head2right The larger the closed loop gain, the more inaccurate the circuit is.
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