Microelectronic Circuits Fourth Edition Adel S. Sedra, Kenneth C. Smith, 1998 Oxford University Press

Transcription

1 Operational Amplifiers LZ lektronik I Microelectronic Circuits Fourth dition Adel S. Sedra, Kenneth C. Smith, 1998 Oxford University Press Dr. Mehmet Siraç Özerdem Department of lectrical and lectronics ngineering Dicle University One of the reasons for the popularity of the Op-amp is its versatility. Circuit symbol for the op amp. 1

2 The op amp shown connected to dc power supplies. Microelectronic Circuits - Fifth dition The ideal op-amp The gain is ideally infinite (Open loop configuration) We will use other components to apply feedback to close the around the op-amp quivalent circuit of the ideal op amp. Microelectronic Circuits - Fifth dition 2

3 Analysis of inverting configuration The inverting closed-loop configuration. Microelectronic Circuits - Fifth dition Analysis of inverting configuration Microelectronic Circuits - Fifth dition 3

4 Analysis of inverting configuration Microelectronic Circuits - Fifth dition Analysis of the inverting configuration taking into account the finite open-loop gain of the op amp. 4

5 xample Dr. Mehmet Siraç Özerdem op amp : ideal a) (v o / v I ) =? b) (v o / v I ) = 100 and R i = 1Mohms. Find the other values of components. Microelectronic Circuits - Fifth dition xample-solution a) Microelectronic Circuits - Fifth dition xample 5

6 Other Application of the Inverting Configuration Dr. Mehmet Siraç Özerdem 1. The inverting configuration with general impedances Z 1 and Z 2 2. The inverting integrator 3. The Op-amp differentiator 4. The weighted summer Microelectronic Circuits - Fifth dition Other Application of the Inverting Configuration 1. The inverting configuration with general impedances Z 1 and Z 2 The inverting configuration with general impedances in the feedback and the feed-in paths. Microelectronic Circuits - Fifth dition 6

7 xample 2 a) (V o (s) / V i (s) )=? Transfer function b) Show that the transfer function is that of a low-pass STC circuit. c) K=? (DC gain) and 3-dB frequency (w o ) =? d) K=40 db f o =1kHz R i =1kΩ Design the circuit (R 1, R 2, C 2?) Microelectronic Circuits - Fifth dition xample-solution 2 Microelectronic Circuits - Fifth dition xample 7

8 Other Application of the Inverting Configuration 2. The inverting integrator Microelectronic Circuits - Fifth dition 2. The inverting integrator Z 1 =R Z 2 =1/sC Frequency response of the integrator xample 8

9 Comparision Dr. Mehmet Siraç Özerdem A low-pass STC circuit The Miller or inverting integrator xample Problem To solve the problem The Miller integrator with a large resistance R F connected in parallel with C in order to provide negative feedback and hence finite gain at dc. 9

10 xample xample R=10kΩ C=10nF a) v o (t) =? b) If the integrator capacitor is shunted by R F =1MΩ resistance, v o (t) =? Microelectronic Circuits - Fifth dition xample xample-solution (a) Input pulse Output linear ramp of ideal integrator with time constant of 0.1 ms. xample 10

11 xample-solution (b) xample Other Application of the Inverting Configuration 3. The Op-amp differentiator 11

12 3. The Op-amp differentiator Dr. Mehmet Siraç Özerdem Frequency response of a differentiator with a time-constant CR. Other Application of the Inverting Configuration 4. The Weighted Summer 12

13 The Noninverting Configuration Microelectronic Circuits - Fifth dition The Noninverting Configuration Analysis of the noninverting circuit. 13

14 The Voltage Follower Dr. Mehmet Siraç Özerdem The unity-gain buffer or follower amplifier. Its equivalent circuit model. xample v o (v 1, v 2 ) =? 14

15 A Difference Amplifier (xample) v o (v I1, v I2 ) =? A Difference Amplifier (xample - Solution) Application of superposition to the analysis of the circuit 15

16 A Difference Amplifier (xample - Solution) Input resistance of the difference amplifier for the case R 3 = R 1 and R 4 = R 2. A Difference Amplifier (xample - Solution) xample Representing the input signals to a differential amplifier in terms of their differential and common-mode components. 16

17 An Instrumentation Amplifier (xample) v o (v I1, v I2 ) =? A Difference Amplifier (xample - Solution) 17