Continuous Time Active Analog Filters

620 Pages·2020·20.774 MB·English

by  Muzaffer Ahmad Siddiqi

Continuous Time Active Analog Filters
Filter circuits play a vital role in diverse applications such as audio/video signal processing,
biomedical devices, instrumentation and control. The replacement of many analog circuits by
digital filters and modules gave the impetus for further advancements in continuous-time as well
as discrete-time analog filters. Today there are important applications such as analog simulation
for retransmission, power quality modulation, and prevention of signal-noise-ration problems in
multistage amplifiers where analog filters are either essential or preferred over digital filters.
This book is conceived as base material for a first course on active network synthesis at the
advanced undergraduate level. It presumes that the reader has already studied basic network
theory and analog electronics. After studying this book the student should be able to select an
appropriate design technique for a specific application and also be equipped for advanced studies
on continuous-time, switched capacitor or current mode filters.
Focusing mainly on continuous-time domain techniques, this text discusses a wide spectrum
of topics. It discusses active filter circuits and their analysis in both frequency and time domains.
It includes practical application-based examples and case studies on topics including medical
instrumentation, audio/video signal processing, anti-aliasing and signal conditioning modules.
More than 130 solved examples and 370 design problems are interspersed throughout the book.
Graphs are plotted throughout the text using the computer simulation tool PSpice.
Muzaffer Ahmad Siddiqi retired as Professor and Chairman from the Department of Electronics
Engineering at Aligarh Muslim University, India. His research includes linear analog integrated
circuits, digital integrated circuits, VLSI design, active network synthesis, microelectronics, and
analog signal processing. He has over 43 years of teaching experience and is the author of the book
Dynamic RAM: Technology Advancements.

Continuous Time Active
Analog Filters
Muzaffer Ahmad Siddiqi
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© Muzaffer Ahmad Siddiqi 2020
This publication is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without the written
permission of Cambridge University Press.
First published in 2020
Printed in India
A catalogue record for this publication is available from the British Library
ISBN 978-1-108-48683-5 Hardback
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and does not guarantee that any content on such websites is, or will remain,
accurate or appropriate.
To the memory of my parents

Contents
Preface xv
Acknowledgments xix
1. Analog Filter: Concepts 1
1.1 Introduction 1
1.2 Network Functions 2
1.2.1 Transfer function 4
1.3 Basic Filtering Action 5
1.3.1 Types of filters 6
1.4 From Passive to Active Filtering 9
1.5 Active RC Filters 11
1.5.1 Active R and active C filters 13
1.6 Sensitivity Concepts 13
1.7 Operational Amplifier 14
1.7.1 Analysis of circuits using operational amplifiers 16
1.8 Integrators Using Operational Amplifiers 17
1.9 Passive Components in Monolithic Filters 19
References 21
Practice Problems 21
viii Contents
2. First- and Second-order Filters 25
2.1 Introduction 25
2.2 First-order Filter Sections 25
2.3 Active First-order Filters 27
2.3.1 Use of inverting amplifiers 27
2.3.2 Bass cut/boost and treble cut/boost filters – application example 29
2.3.3 Fluorescence spectroscopy: application example 32
2.3.4 Use of non-inverting amplifiers 35
2.4 Effect of Operational Amplifier’s Pole on Integrators 37
2.5 Biquadratic Section: Parameters w and Q 42
o o
2.6 Responses of Second-order Filter Sections 44
2.7 Second-order Low Pass Response 44
2.7.1 Earthworm seismic data acquisition: application example 48
2.8 Second-order High Pass Response 49
2.9 Second-order Band Pass Response 51
2.10 Band Reject (BR) Response 55
2.11 Second-order All Pass Response 57
2.12 Effect of Operational Amplifier’s Pole on Biquads 58
References 59
Practice Problems 59
3. Magnitude Approximations 63
3.1 Introduction 63
3.2 Magnitude Approximations 64
3.3 Maximally Flat – Butterworth Approximation 66
3.3.1 Design of low pass Butterworth filter 69
3.3.2 Use of lossless ladder 70
3.4 Equal-ripple Approximations 74
3.5 Chebyshev Approximation 75
3.5.1 Low pass Chebyshev filter design 75
3.6 Inverse Chebyshev Approximations 79
3.6.1 Design of an inverse Chebyshev filter 81
3.7 Cauer or Elliptic Approximation 86
3.7.1 Design of Cauer filters 87
3.8 Maximally Flat Pass Band with Finite Zeros 95
References 97
Practice Problems 97