Analysis and Application of Analog Electronic Circuits to Biomedical Instrumentation

556 Pages·2003·2.865 MB·English

by  Robert B. Northrop

Analysis and Application
of Analog Electronic
Circuits to Biomedical
Instrumentation
© 2004 by CRC Press LLC
Biomedical Engineering
Series
Edited by Michael R. Neuman
Published Titles
Electromagnetic Analysis and Design in Magnetic Resonance
Imaging, Jianming Jin
Endogenous and Exogenous Regulation and
Control of Physiological Systems, Robert B. Northrop
Artificial Neural Networks in Cancer Diagnosis, Prognosis,
and Treatment, Raouf N.G. Naguib and Gajanan V. Sherbet
Medical Image Registration, Joseph V. Hajnal, Derek Hill, and
David J. Hawkes
Introduction to Dynamic Modeling of Neuro-Sensory Systems,
Robert B. Northrop
Noninvasive Instrumentation and Measurement in Medical
Diagnosis, Robert B. Northrop
Handbook of Neuroprosthetic Methods, Warren E. Finn
and Peter G. LoPresti
Signals and Systems Analysis in Biomedical Engineering,
Robert B. Northrop
Angiography and Plaque Imaging: Advanced Segmentation
Techniques, Jasjit S. Suri and Swamy Laxminarayan
Analysis and Application of Analog Electronic Circuits to
Biomedical Instrumentation, Robert B. Northrop
© 2004 by CRC Press LLC
The BIOMEDICAL ENGINEERING Series
Series Editor Michael R. Neuman
Analysis and Application
of Analog Electronic
Circuits to Biomedical
Instrumentation
Robert B. Northrop
CRC PR ESS
Boca Raton London New York Washington, D.C.
© 2004 by CRC Press LLC
Library of Congress Cataloging-in-Publication Data
Northrop, Robert B.
Analysis and application of analog electronic circuits to biomedical instrumentation / by
Robert B. Northrop.
p. cm. — (Biomedical engineering series)
Includes bibliographical references and index.
ISBN 0-8493-2143-3 (alk. paper)
1. Analog electronic systems. 2. Medical electronics. I. Title. II. Biomedical engineering
series (Boca Raton, Fla.)
TK7867.N65 2003
610¢.28—dc22 2003065373
This book contains information obtained from authentic and highly regarded sources. Reprinted material
is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable
efforts have been made to publish reliable data and information, but the author and the publisher cannot
assume responsibility for the validity of all materials or for the consequences of their use.
Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic
or mechanical, including photocopying, microfilming, and recording, or by any information storage or
retrieval system, without prior permission in writing from the publisher.
The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for
creating new works, or for resale. Specific permission must be obtained in writing from CRC Press LLC
for such copying.
Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431.
Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are
used only for identification and explanation, without intent to infringe.
Visit the CRC Press Web site at www.crcpress.com
© 2004 by CRC Press LLC
No claim to original U.S. Government works
International Standard Book Number 0-8493-2143-3
Library of Congress Card Number 2003065373
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
Printed on acid-free paper
© 2004 by CRC Press LLC
Dedication
I dedicate this text to my wife and daughters: Adelaide, Anne, Kate, and Victoria.
© 2004 by CRC Press LLC
Preface
Reader Background
This text is intended for use in a classroom course on analysis and application
of analog electronic circuits in biomedical engineering taken by junior or
senior undergraduate students specializing in biomedical engineering. It will
also serve as a reference book for biophysics and medical students interested
in the topics. Readers are assumed to have had introductory core courses
up to the junior level in engineering mathematics, including complex alge-
bra, calculus, and introductory differential equations. They also should have
taken an introductory course in electronic circuits and devices. As a result
of taking these courses, readers should be familiar with systems block dia-
grams and the concepts of frequency response and transfer functions; they
should be able to solve simple linear ordinary differential equations and
perform basic manipulations in linear algebra. It is also important to have
an understanding of the working principles of the various basic solid-state
devices (diodes, bipolar junction transistors, and field-effect transistors) used
in electronic circuits in biomedical applications.
Rationale
The interdisciplinary field of biomedical engineering is demanding in that
it requires its followers to know and master not only certain engineering
skills (electronics, materials, mechanical, photonic), but also a diversity of
material in the biological sciences (anatomy, biochemistry, molecular biology,
genomics, physiology, etc.). This text was written to aid undergraduate bio-
medical engineering students by helping them to understand the basic ana-
log electronic circuits used in signal conditioning in biomedical
instrumentation. Because many bioelectric signals are in the microvolt range,
noise from electrodes, amplifiers, and the environment is often significant
compared to the signal level. This text introduces the basic mathematical
tools used to describe noise and how it propagates through linear systems.
It also describes at a basic level how signal-to-noise ratio can be improved
by signal averaging and linear filtering.
vii
© 2004 by CRC Press LLC
viii Analysis and Application of Analog Electronic Circuits
Bandwidths associated with endogenous (natural) biomedical signals
range from dc (e.g., hormone concentrations or dc potentials on the body
surface) to hundreds of kilohertz (bat ultrasound). Exogenous signals asso-
ciated with certain noninvasive imaging modalities (e.g., ultrasound, MRI)
can reach into the tens of megahertz. Throughout the text, op amps are
shown to be the keystone of modern analog signal conditioning system
design. This text illustrates how op amps can be used to build instrumenta-
tion amplifiers, isolation amplifiers, active filters, and many other systems
and subsystems used in biomedical instrumentation.
The text was written based on the author’s experience in teaching courses
in electronic devices and circuits, electronic circuits and applications, and
biomedical instrumentation for over 35 years in the electrical and computer
engineering department at the University of Connecticut, as well as on his
personal research in biomedical instrumentation.
Description of the Chapters
Analysis and Application of Analog Electronic Circuits in Biomedical Engineering
is organized into 12 chapters, an index, and a reference section. Extensive
examples in the chapters are based on electronic circuit problems in biomed-
ical engineering.
In Chapter 1, Sources and Properties of Biomedical Signals, the sources of
bioelectric phenomena in nerves and muscles are described. The
general characteristics of biomedical signals are set forth and we
examine the general properties of physiological systems, including
nonlinearity and nonstationarity.
In Chapter 2, Models for Semiconductor Devices Used in Analog Electronic
Systems, we describe the mid- and high-frequency models used for
analysis of pn junction diodes, BJTs, and FETs in electronic circuits.
The high-frequency behavior of basic one- and two-transistor am-
plifiers is treated and the Miller effect is introduced. This chapter
also describes the properties of photodiodes, photoconductors,
LEDs, and laser diodes.
In Chapter 3, The Differential Amplifier, this important analog electronic
circuit architecture is analyzed for BJT and FET DAs. Mid- and high-
frequency behavior is treated, as well as the factors that lead to a
desirable high common-mode rejection ratio. DAs are shown to be
essential subcircuits in all op amps, comparators, and instrumenta-
tion amplifiers.
© 2004 by CRC Press LLC
Preface ix
In Chapter 4, General Properties of Electronic Single-Loop Feedback Systems,
we introduce the four basic kinds of electronic feedback (positive/
negative voltage feedback and positive/negative current feedback)
and describe how they affect linear amplifier performance.
Chapter 5, Feedback, Frequency Response, and Amplifier Stability, presents
Bode plots and the root-locus technique as design tools and means
of predicting closed-loop system stability. The effects of negative
voltage and current feedback, as well as positive voltage feedback,
on an amplifier’s gain and bandwidth, and input and output imped-
ance are described. The design of certain “linear” oscillators is treated.
In Chapter 6, Operational Amplifiers, we examine the properties of the
ideal op amp and how its model can be used in quick pencil-and-
paper circuit analysis of various op amp circuits. Circuit models for
various types of practical op amps are described, including current
feedback op amps. Gain-bandwidth products are shown to differ for
different op amp types and circuits. Analog voltage comparators are
introduced and practical circuit examples are given. The final sub-
section illustrates some applications of op amps in biomedical
instrumentation.
In Chapter 7, Analog Active Filters, we illustrate three major architectures
easily used to design for op amp-based active filters. These include
the Sallen and Key quadratic AF, the one- and two-loop biquad AF,
and the GIC-based AF. Voltage and digitally tunable AF designs are
described and examples are given; AF applications are discussed.
In Chapter 8, Instrumentation and Medical Isolation Amplifiers, we describe
the general properties of instrumentation amplifiers (IAs) and some
of the circuit architectures used in their design. Medical isolation
amplifiers (MIAs) are shown to be necessary to protect patients from
electrical shock hazard during bioelectric measurements. All MIAs
provide extreme galvanic isolation between the patient and the mon-
itoring station. We illustrate several MIA architectures, including a
novel direct sensing system that uses the giant magnetoresistive
effect. Also described are the current safety standards for MIAs.
In Chapter 9, Noise and the Design of Low-Noise Amplifiers for Biomedical
Applications, descriptors of random noise, such as the probability
density function; the auto- and cross-correlation functions; and the
auto- and cross-power density spectra, are introduced and their
properties discussed. Sources of random noise in active and passive
components are presented and we show how noise propagates sta-
tistically through LTI filters. Noise factor, noise figure, and signal-
to-noise ratio are shown to be useful measures of a signal condition-
ing system’s noisiness. Noise in cascaded amplifier stages, DAs, and
feedback amplifiers is treated. Examples of noise-limited signal
© 2004 by CRC Press LLC
x Analysis and Application of Analog Electronic Circuits
resolution calculations are given. Factors affecting the design of low-
noise amplifiers and a list of low-noise amplifiers are presented.
Digital Interfaces, Chapter 10, details these particular interfaces, as well
as derivation of aliasing and the sampling theorem. Analog-to-dig-
ital and digital-to-analog converters are described. Hold circuits and
quantization noise are also treated.
In Chapter 11, Modulation and Demodulation of Bioelectric Signals, we
illustrate the basics of modulation schemes used in instrumentation
and biotelemetry systems. Analysis is conducted on AM; single-
sideband AM (SSBAM); double-sideband suppressed carrier (DSBSC)
AM; angle modulation including phase and frequency modulation
(FM); narrow-band FM; delta modulation; and integral pulse fre-
quency modulation (IPFM) systems, as well as on means for their
demodulation.
In Chapter 12, Examples of Special Analog Circuits and Systems in Biomed-
ical Instrumentation, we describe and analyze circuits and systems
important in biomedical and other branches of instrumentation.
These include the phase-sensitive rectifier; phase detector circuits;
voltage- and current-controlled oscillators, including VFCs and
VPCs, phase-locked loops, and applications; true RMS converters;
IC thermometers; and four examples of complex measurement sys-
tems developed by the author.
In addition, the comprehensive references at the end of the book contain
entries from periodicals, the World Wide Web, and additional texts.
Features
Some of the unique contents of this text are:
• Section 2.6 in Chapter 2 describes the properties of photonic sensors
and emitters, including PIN and avalanche photodiodes, and pho-
toconductors. Signal conditioning circuits for these sensors are given
and analyzed. This section also describes the properties of LEDs and
laser diodes, as well as the circuits required to power them.
• Chapter 8 gives a thorough treatment of the design of instrumenta-
tion amplifiers and medical isolation amplifiers. Also described in
detail are current safety standards for MIAs.
• A comprehensive treatment of noise in analog signal conditioning
systems is given in Chapter 9.
© 2004 by CRC Press LLC
Preface xi
• Chapter 10 on digital interfaces examines the designs of many types
of ADCs and DACs and introduces aliasing and quantization noise
as possible costs for going to or from analog or digital domains.
• Chapter 11 illustrates the use of phase-locked loops to generate or
demodulate angle-modulated signals, including phase and fre-
quency modulation as well as AM and DSBSCM signals.
• Chapter 12 describes an applications-oriented collection of analog
circuit “building blocks,” including: phase-sensitive rectifiers; phase
detectors; phase-locked loops; VCOs and ICOs, including VFCs and
VPCs; true RMS converters; IC thermometers; and examples of com-
plex biomedical instrument systems designed by the author that use
op amps extensively.
• Many illustrative examples from medical electronics are given in the
chapters.
• Home problems that accompany each chapter (except Chapter 1,
Chapter 8, and Chapter 12) stress biomedical electronic applications.
Robert B. Northrop
Chaplin, Connecticut
© 2004 by CRC Press LLC