Analysis and Application of Analog Electronic Circuits to Biomedical Instrumentation

574 Pages·2012·7.21 MB·English

by  Robert B. Northrop

K12982_cover 2/2/12 1:19 PM Page 1
C M Y CM MY CY CMY K
BIOMEDICAL ENGINEERING
NORTHROP
SECOND EDITION
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ANALYSIS AND APPLICATION OF A
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ANALOG ELECTRONIC
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CIRCUITS TO BIOMEDICAL INSTRUMENTATION

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Analysis and Application of Analog Electronic Circuits to Biomedical Instrumentation, T

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Second Edition helps biomedical engineers understand the basic analog electronic circuits used
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for signal conditioning in biomedical instruments. It explains the function and design of signal B P
conditioning systems using analog ICs—the circuits that enable ECG, EEG, EMG, ERG, tomographic IO L
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images, biochemical spectrograms, and other crucial medical applications. M
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This book demonstrates how op amps are the keystone of modern analog signal conditioning O
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system design and illustrates how they can be used to build instrumentation amplifiers, active filters, N
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and many other biomedical instrumentation systems and subsystems. It introduces the mathematical
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tools used to describe noise and its propagation through linear systems, and it looks at how signal- IN F
to-noise ratios can be improved by signal averaging and linear filtering. S A
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Features U A
•Analyzes the properties of photonic sensors and emitters and the circuits that power them M L
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•Details the design of instrumentation amplifiers and medical isolation amplifiers EN G
•Considers the modulation and demodulation of biomedical signals T E
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•Examines analog power amplifiers, including power op amps and class D (switched) PAs L
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•Describes wireless patient monitoring, including Wi-Fi and Bluetooth communication protocols IO C
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•Explores RFID, GPS, and ultrasonic tags and the design of fractal antennas R
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•Addresses special analog electronic circuits and systems such as phase-sensitive rectifiers,
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phase detectors, and IC thermometers
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By explaining the “building blocks” of biomedical systems, the author illustrates the importance
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of signal conditioning systems in the devices that gather and monitor patients’ critical medical
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information. Fully revised and updated, this second edition includes new chapters, a glossary, and U
end-of-chapter problems. I
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SECOND
K12982 EDITION
The BIOMEDICAL ENGINEERING Series
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SECOND EDITION
ANALYSIS AND
APPLICATION OF
ANALOG ELECTRONIC
CIRCUITS TO BIOMEDICAL
INSTRUMENTATION
Michael R. Neuman, Series Editor
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Biomedical Engineers, Robert B. Northrop and Anne N. Connor
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Jeffrey O. Hollinger
Analysis and Application of Analog Electronic Circuits to Biomedical
Instrumentation, Second Edition, Robert B. Northrop
SECOND EDITION
ANALYSIS AND
APPLICATION OF
ANALOG ELECTRONIC
CIRCUITS TO BIOMEDICAL
INSTRUMENTATION
ROBERT B. NORTHROP
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
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Contents
List of Figures ................................................................................................................................xiii
Preface..........................................................................................................................................xxxv
Author .........................................................................................................................................xxxix
Chapter 1 Sources and Properties of Biomedical Signals ............................................................1
1.1 Introduction .......................................................................................................1
1.2 Sources of Endogenous Bioelectric Signals ......................................................1
1.3 Nerve Action Potentials .....................................................................................2
1.4 Muscle Action Potentials ...................................................................................4
1.4.1 Introduction ..........................................................................................4
1.4.2 The Origin of EMGs ............................................................................4
1.4.3 EMG Amplifiers ...................................................................................7
1.5 Electrocardiogram .............................................................................................7
1.5.1 Introduction ..........................................................................................7
1.5.2 ECG Amplifiers ....................................................................................8
1.6 Other Biopotentials ............................................................................................9
1.6.1 Introduction ..........................................................................................9
1.6.2 EEGs.....................................................................................................9
1.6.3 Other Body Surface Potentials ...........................................................10
1.6.4 Discussion...........................................................................................10
1.7 Electrical Properties of Bioelectrodes .............................................................10
1.8 Exogenous Bioelectric Signals ........................................................................13
1.9 Chapter Summary ...........................................................................................15
Chapter 2 Properties and Models of Semiconductor Devices Used in Analog
Electronic Systems .....................................................................................................17
2.1 Introduction .....................................................................................................17
2.2 pn Junction Diodes ..........................................................................................17
2.2.1 Introduction ........................................................................................17
2.2.2 pn Diode’s Volt–Ampere Curve .........................................................18
2.2.3 High-Frequency Behavior of Diodes ..................................................20
2.2.4 Schottky Diodes .................................................................................23
2.3 Midfrequency Models for BJT Behavior .........................................................25
2.3.1 Introduction ........................................................................................25
2.3.2 Midfrequency Small-Signal Models for BJTs ....................................27
2.3.3 Amplifiers Using One BJT .................................................................31
2.3.4 Simple Amplifiers Using Two Transistors at Midfrequencies ...........35
2.3.5 Use of Transistor Dynamic Loads to Improve
Amplifier Performance .......................................................................41
2.4 Midfrequency Models for Field-Effect Transistors .........................................44
2.4.1 Introduction ........................................................................................44
2.4.2 JFETs at Midfrequencies ....................................................................45
2.4.3 MOSFET Behavior at Midfrequencies...............................................48
v
vi Contents
2.4.4 Basic, Midfrequency, Single FET Amplifiers ....................................50
2.4.5 Simple Amplifiers Using Two FETs at Midfrequencies .....................53
2.5 High-Frequency Models for Transistors and Simple
Transistor Amplifiers ...............................................................................57
2.5.1 Introduction ........................................................................................57
2.5.2 High-Frequency SSMs for BJTs and FETs ........................................59
2.5.3 Behavior of One-BJT and One-FET Amplifiers at
High Frequencies ................................................................................63
2.5.4 High-Frequency Behavior of Two-Transistor Amplifiers ...................72
2.5.5 Broadbanding Strategies ....................................................................76
2.6 Photons, Photodiodes, Photoconductors, LEDs, and Laser Diodes ................78
2.6.1 Introduction ........................................................................................78
2.6.2 PIN Photodiodes .................................................................................79
2.6.3 Avalanche Photodiodes ......................................................................84
2.6.4 Signal Conditioning Circuits for Photodiodes ...................................87
2.6.5 Photoconductors .................................................................................90
2.6.6 LEDs...................................................................................................93
2.6.7 Laser Diodes .......................................................................................94
2.7 Chapter Summary .........................................................................................102
Chapter 3 Differential Amplifier ..............................................................................................111
3.1 Introduction ...................................................................................................111
3.2 DA Circuit Architecture ................................................................................111
3.3 Common-Mode Rejection Ratio ....................................................................114
3.4 CM and DM Gain of Simple DA Stages at High Frequencies ......................116
3.4.1 Introduction ......................................................................................116
3.4.2 High-Frequency Behavior of A and A for the JFET DA ..............117
C D
3.4.3 High-Frequency Behavior of A and A for the BJT DA ................120
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3.5 Input Resistance of Simple Transistor DAs ...................................................121
3.6 How Signal Source Impedance Affects the Low-Frequency CMRR ...........123
3.7 How Op Amps Can be Used to Make DAs for Medical Applications ..........127
3.7.1 Introduction ......................................................................................127
3.7.2 Op Amp DA Designs for Instrumentation .......................................127
3.8 Chapter Summary .........................................................................................129
Chapter 4 General Properties of Electronic, Single-Loop Feedback Systems .........................139
4.1 Introduction ...................................................................................................139
4.2 Classification of Electronic Feedback Systems .............................................139
4.3 Some Effects of Negative Voltage Feedback .................................................140
4.3.1 Reduction of Output Resistance .......................................................140
4.3.2 Reduction of Total Harmonic Distortion..........................................142
4.3.3 Increase of NFB Amplifier Bandwidth at the Cost of Gain .............143
4.3.4 Decrease in Gain Sensitivity ............................................................146
4.4 Effects of Negative Current Feedback...........................................................148
4.5 Positive Voltage Feedback .............................................................................151
4.5.1 Introduction ......................................................................................151
4.5.2 Amplifier with Capacitance Neutralization .....................................151
4.6 Chapter Summary .........................................................................................154
Contents vii
Chapter 5 Feedback, Frequency Response, and Amplifier Stability ........................................161
5.1 Introduction ...................................................................................................161
5.2 Review of Amplifier Frequency Response ....................................................161
5.2.1 Introduction ......................................................................................161
5.2.2 Bode Plots .........................................................................................162
5.3 What Is Meant by Feedback System Stability ...............................................165
5.4 Use of Root Locus in Feedback Amplifier Design ........................................173
5.5 Use of Root Locus in the Design of “Linear” Oscillators .............................180
5.5.1 Introduction ......................................................................................180
5.5.2 Phase-Shift Oscillator ......................................................................182
5.5.3 Wien Bridge Oscillator .....................................................................184
5.6 Chapter Summary .........................................................................................186
Chapter 6 Operational Amplifiers and Comparators ................................................................193
6.1 Ideal Op Amp ................................................................................................193
6.1.1 Introduction ......................................................................................193
6.1.2 Properties of Ideal Op Amps............................................................194
6.1.3 Some Examples of Op Amp Circuits Analyzed Using IOAs ...........194
6.2 Practical Op Amps ........................................................................................198
6.2.1 Introduction ......................................................................................198
6.2.2 Functional Categories of Real Op Amps .........................................198
6.3 Gain-Bandwidth Relations for Voltage-Feedback OAs .................................200
6.3.1 GBWP of an Inverting Summer .......................................................200
6.3.2 GBWP of a Noninverting Voltage-Feedback OA.............................201
6.4 Gain-Bandwidth Relations in Current Feedback Amplifiers ........................202
6.4.1 Noninverting Amplifier Using a CFOA ...........................................202
6.4.2 Inverting Amplifier Using a CFOA ..................................................203
6.4.3 Limitations of CFOAs ......................................................................204
6.5 Analog Voltage Comparators ........................................................................206
6.5.1 Introduction ......................................................................................206
6.5.2 Applications of Voltage Comparators ..............................................209
6.5.3 Discussion.........................................................................................211
6.6 Some Applications of Op Amps in Biomedicine ..........................................212
6.6.1 Introduction ......................................................................................212
6.6.2 Analog Integrators and Differentiators ............................................213
6.6.3 Charge Amplifiers ............................................................................215
6.6.4 A Two-Op Amp, ECG Amplifier .....................................................217
6.7 Chapter Summary .........................................................................................218
Chapter 7 Introduction to Analog Active Filters ......................................................................225
7.1 Introduction ...................................................................................................225
7.2 Active Filter Applications ..............................................................................226
7.3 Types of Analog Active Filters ......................................................................226
7.3.1 Introduction ......................................................................................226
7.3.2 Sallen & Key, Controlled-Source AFs .............................................226
7.3.3 Biquad Active Filters ........................................................................230
7.3.4 Generalized Impedance Converter AFs ...........................................234
7.3.5 Choice of AF Components ...............................................................238
viii Contents
7.4 Electronically Tunable AFs ...........................................................................239
7.4.1 Introduction ......................................................................................239
7.4.2 A Tunable, Two-Loop Biquad LPF ..................................................240
7.4.3 Use of Digitally Controlled Potentiometers to Tune a
Sallen & Key LPF ............................................................................242
7.5 Chapter Summary .........................................................................................243
Chapter 8 Instrumentation and Medical Isolation Amplifiers ..................................................249
8.1 Introduction ...................................................................................................249
8.2 Instrumentation Amps ...................................................................................250
8.3 Medical Isolation Amps ................................................................................251
8.3.1 Introduction ......................................................................................251
8.3.2 Common Types of Medical Isolation Amplifiers .............................252
8.3.3 A Prototype Magnetic MIA .............................................................256
8.4 Safety Standards in Medical Electronic Amplifiers ......................................259
8.4.1 Introduction ......................................................................................259
8.4.2 Certification Criteria for Medical Electronic Systems .....................260
8.5 Medical-Grade Power Supplies .....................................................................263
8.6 Chapter Summary .........................................................................................264
Chapter 9 Noise and the Design of Low-Noise Signal Conditioning Systems for
Biomedical Applications ..........................................................................................265
9.1 Introduction ...................................................................................................265
9.2 Descriptors of Random Noise in Biomedical Measurement Systems ...........266
9.2.1 Introduction ......................................................................................266
9.2.2 Probability Density Function ...........................................................266
9.2.3 Autocorrelation Function and the Power Density Spectrum ............268
9.2.4 Sources of Random Noise in Signal Conditioning Systems ............270
9.2.4.1 Noise from Resistors .........................................................271
9.2.4.2 Two-Source Noise Model for Active Devices ..................274
9.2.4.3 Noise in JFETs ..................................................................275
9.2.4.4 Noise in BJTs ....................................................................276
9.3 Propagation of Noise through LTI Filters .....................................................277
9.4 Noise Factor and Figure of Amplifiers ..........................................................279
9.4.1 Broadband Noise Factor and Noise Figure of Amplifiers ................279
9.4.2 Spot Noise Factor and Figure ...........................................................280
9.4.3 Transformer Optimization of Amplifier NF and Output
SNR ................................................................................................282
9.5 Cascaded Noisy Amplifiers ...........................................................................284
9.5.1 Introduction ......................................................................................284
9.5.2 SNR of Cascaded, Noisy Amplifiers ................................................284
9.6 Noise in Differential Amplifiers ....................................................................285
9.6.1 Introduction ......................................................................................285
9.6.2 Calculation of the SNR of the DA ..................................................286
o
9.7 Effect of Feedback on Noise..........................................................................287
9.7.1 Introduction ......................................................................................287
9.7.2 Calculation of SNR of an Amplifier with NVFB ...........................287
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Contents ix
9.8 Examples of Noise-Limited Resolution of Certain Signal
Conditioning Systems ....................................................................................288
9.8.1 Introduction ......................................................................................288
9.8.2 Calculation of the Minimum Resolvable AC Input Voltage to a
Noisy Op Amp .................................................................................289
9.8.3 Calculation of the Minimum Resolvable AC Input Signal to
Obtain a Specified SNR in a Transformer-Coupled Amplifier .......290
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9.8.4 Effect of Capacitance Neutralization on the SNR of an
o
Electrometer Amplifier Used for Glass Micropipette,
Intracellular, Transmembrane Voltage Recording ...........................291
9.8.5 Calculation of the Smallest Resolvable ∆R/R in a Wheatstone
Bridge Determined by Noise ............................................................294
9.8.5.1 Introduction ......................................................................294
9.8.5.2 Bridge Sensitivity Calculations ........................................294
9.8.5.3 Bridge SNR ......................................................................294
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9.8.6 Calculation of SNR Improvement Using a Lock-In Amplifier ........295
9.8.7 Signal-to-Noise Ratio Improvement by Signal Averaging of
Evoked Transient Signals .................................................................299
9.8.7.1 Introduction ......................................................................299
9.8.7.2 Analysis of SNR Improvement by Averaging ..................300
9.8.7.3 Discussion .........................................................................303
9.9 Some Low-Noise Amplifiers .........................................................................304
9.10 Art of Low-Noise Signal Conditioning System Design ................................304
9.11 Chapter Summary .........................................................................................307
Chapter 10 Digital Interfaces ......................................................................................................315
10.1 Introduction ...................................................................................................315
10.2 Aliasing and the Sampling Theorem .............................................................315
10.2.1 Introduction ......................................................................................315
10.2.2 Sampling Theorem ...........................................................................315
10.3 Digital-to-Analog Converters ........................................................................319
10.3.1 Introduction ......................................................................................319
10.3.2 DAC Designs ....................................................................................319
10.3.3 Static and Dynamic Characteristics of DACs ..................................323
10.4 Sample-and-Hold Circuits .............................................................................326
10.5 Analog-to-Digital Converters ........................................................................327
10.5.1 Introduction ......................................................................................327
10.5.2 Tracking (Servo) ADC .....................................................................328
10.5.3 Successive Approximation ADC ......................................................329
10.5.4 Integrating Converters ......................................................................330
10.5.5 Flash Converters ...............................................................................334
10.5.6 Delta–Sigma ADCs ..........................................................................337
10.6 Quantization Noise ........................................................................................341
10.7 Chapter Summary .........................................................................................345
Chapter 11 Modulation and Demodulation of Biomedical Signals ............................................349
11.1 Introduction ...................................................................................................349
11.2 Modulation of a Sinusoidal Carrier Viewed in the Frequency Domain ........350