The Fields of Electronics: Understanding Electronics Using Basic Physics

201 Pages·2002·1.839 MB·English

by  Ralph Morrison

THE FIELDS OF
ELECTRONICS
THE FIELDS OF
ELECTRONICS
Understanding Electronics
Using Basic Physics
Ralph Morrison
A Wiley-Interscience Publication
JOHN WILEY & SONS, INC.
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Copyright c 2002byJohnWiley&Sons,Inc.,NewYork.Allrightsreserved.
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CONTENTS
Preface xi
1 The Electric Field 1
1.1 Introduction 1
1.2 Charge 2
1.3 Electrical Forces on Charged Bodies 3
1.4 Electric Field 4
1.5 Work 5
1.6 Voltage 6
1.7 Charges on Surfaces 6
1.8 Equipotential Surfaces 8
1.9 Field Units 8
1.10 Batteries—A Voltage Source 10
1.11 Current 11
1.12 Resistors 12
1.13 Resistors in Series or Parallel 13
1.14 E Field and Current Flow 15
1.15 Problems 15
1.16 Energy Transfer 16
1.17 Resistor Dissipation 17
1.18 Problems 17
1.19 Electric Field Energy 18
1.20 Ground and Ground Planes 19
1.21 Induced Charges 20
1.22 Forces and Energy 20
1.23 Problems 21
1.24 Review 21
2 Capacitors, Magnetic Fields, and Transformers 23
2.1 Dielectrics 23
2.2 Displacement Field 23
vi CONTENTS
2.3 Capacitance 25
2.4 Capacitance of Two Parallel Plates 25
2.5 Capacitance in Space 26
2.6 Current Flow in Capacitors 27
2.7 RC Time Constant 28
2.8 Problems 29
2.9 Shields 30
2.10 Magnetic Field 31
2.11 Solenoids 32
2.12 Ampe`re’s Law 32
2.13 Problems 34
2.14 Magnetic Circuit 34
2.15 Induction or B Field 34
2.16 Magnetic Circuit without a Gap 36
2.17 Magnetic Circuit with a Gap 38
2.18 Transformer Action 39
2.19 Magnetic Field Energy 40
2.20 Inductors 41
2.21 L=R Time Constant 42
2.22 Mutual Inductance 43
2.23 Problems 44
2.24 Review 44
3 Utility Power and Circuit Concepts 46
3.1 Sine Waves 46
3.2 Reactance and Impedance 47
3.3 Problems 50
3.4 Resonance 50
3.5 Phase 52
3.6 Parallel RL and RC Circuits 53
3.7 Problems 54
3.8 RMS Values 54
3.9 Problems 55
3.10 Transmission Lines 56
3.11 Poynting’s Vector 57
3.12 Transmission Line over an Equipotential Surface 58
3.13 Transmission Lines and Sine Waves 59
3.14 Coaxial Transmission 61
3.15 Utility Power Distribution 62
CONTENTS vii
3.16 Earth as a Conductor 64
3.17 Power Transformers in Electronic Hardware 65
3.18 Electrostatic Shields in Electronic Hardware 67
3.19 Where to Connect the Metal Box 69
3.20 Problems 73
3.21 Review 74
4 A Few More Tools 75
4.1 Introduction 75
4.2 Resistivity 75
4.3 Inductance of Isolated Conductors 76
4.4 Ohms per Square 77
4.5 Problems 77
4.6 Radiation 77
4.7 Half-Dipole Antennas 78
4.8 Current Loop Radiators 80
4.9 Field Energy in Space 82
4.10 Problems 82
4.11 Reflection 83
4.12 Skin Effect 84
4.13 Problems 84
4.14 Surface Currents 85
4.15 Ground Planes and Fields 86
4.16 Apertures 86
4.17 Multiple Apertures 87
4.18 Waveguides 88
4.19 Attenuation of Fields by a Conductive Enclosure 88
4.20 Gaskets 89
4.21 Honeycombs 89
4.22 Wave Coupling into Circuits 90
4.23 Problems 91
4.24 Square Waves 91
4.25 Harmonic Content in Utility Power 94
4.26 Spikes and Pulses 95
4.27 Transformers 96
4.28 Eddy Currents 98
4.29 Ferrite Materials 99
viii CONTENTS
4.30 Problems 99
4.31 Review 100
5 Analog Design 101
5.1 Introduction 101
5.2 Analog Signals 101
5.3 Common-Mode Interference 102
5.4 Common-Mode Rejection in Instrumentation 106
5.5 Problems 107
5.6 Voltage Measurement: Oscilloscopes 107
5.7 Microphones 108
5.8 Resistors 109
5.9 Guard Rings 110
5.10 Capacitors 111
5.11 Problems 112
5.12 Feedback Processes 113
5.13 Problems 115
5.14 Miller Effect 115
5.15 Inductors 116
5.16 Transformers 117
5.17 Problems 119
5.18 Isolation Transformers 120
5.19 Solenoids and Relays 121
5.20 Problems 122
5.21 Power Line Filters 123
5.22 Request for Energy 124
5.23 Filter and Energy Requests 125
5.24 Power Line Filters above 1 MHz 125
5.25 Mounting the Filter 125
5.26 Optical Isolators 127
5.27 Hall Effect 127
5.28 Surface Effects 127
5.29 Review 127
6 Digital Design and Mixed Analog/Digital Design 129
6.1 Introduction 129
6.2 Logic and Transmission Lines 129
6.3 Decoupling Capacitors 130
6.4 Ground Planes 131
CONTENTS ix
6.5 Power Planes 132
6.6 Decoupling Power Geometries 132
6.7 Ground Plane Islands 133
6.8 Radiation from Loops 133
6.9 Problems 133
6.10 Leaving the Board 134
6.11 Ribbon Cable and Common-Mode Coupling 135
6.12 Braided Cable Shields 135
6.13 Transfer Impedance 137
6.14 Mechanical Cable Terminations 138
6.15 Problems 138
6.16 Mounting Power Transistors 139
6.17 Electrostatic Discharge 139
6.18 ESD Precautions 141
6.19 Zapping 141
6.20 Product Testing: Radiation 142
6.21 Military Testing 142
6.22 Chattering Relay Test 143
6.23 Euro Standards 143
6.24 LISN 144
6.25 Sniffers 144
6.26 Simple Antenna 145
6.27 Peripherals 145
6.28 Problems 146
6.29 Lightning 146
6.30 Problems 147
6.31 Mixing Analog and Digital Design 147
6.32 Ground Bounce 148
6.33 Review 148
7 Facilities and Sites 149
7.1 Introduction 149
7.2 Utility Power 149
7.3 Floating Utility Power 151
7.4 Isolated Grounds 152
7.5 Single-Point Grounding 153
7.6 Ground Planes 155
7.7 Alternative Ground Planes 156
7.8 Power Centers 157
x CONTENTS
7.9 Lightning Protection 158
7.10 Surge Suppression 160
7.11 Racks 161
7.12 Magnet Fields around Distribution Transformers 161
7.13 Monitor Fields 162
7.14 Motor Controllers 162
7.15 Screen Rooms 163
7.16 Review 164
Appendix I: Solutions to Problems 165
Appendix II: Glossary of Common Terms 177
Appendix III: Abbreviations 183
Index 187
PREFACE
This book provides a new way to understand the subject of electronics. The
central theme is that all electrical phenomena can be explained in terms of
electric and magneticfields.Beginning studentsplacetheir faith in their early
instruction. They assume that the way they have been educated is the best
way. Any departure from this format just adds complications. This book is a
departure—hopefully, one that helps.
There are many engineers and scientists struggling to function in the real
world.Theireducationdidnotpreparethemforhandlingmostofthepractical
problems they encounter. The practitioner in trouble with grounds, noise,and
interferencefeelsthatsomethingismissinginhiseducation.Thenewengineer
has a very difficult time ordering, specifying, or using hardware correctly.
Facilities and power distribution are a mystery. Surprisingly, all these areas
areaccessibleoncethecorrectviewpointistaken.Thisbook hasbeen written
to provideabetterintroductiontothefield ofelectronicsso thatthepartsthat
are often omitted can be put into perspective.
The book uses very little mathematics. It helps to have some background in
electronics,butitisnotnecessary.Thebeginningstudentmayneedsomehelp
from an instructor to fill in some of the blanks. The practicing engineer will
be able to read this book with ease.
Field phenomena are often felt to be the domain of the physicist. In a
sense this is correct. Unfortunately, without a field-based understanding,
many electronic processes must remain mysteries. It is not necessary to solve
difficult problems to have an appreciation of how things work. It is only nec-
essary to appreciate the fundamentals and understand the true nature of the
world.
Toillustratetheproblem,consideranelectricfieldthatisconstanteverywhere.
Place a conducting loop of wire at some crazy angle in this field and ask a
question: What is the shape of the new field? This is a very difficult problem
even with a great deal of computing power. Now, have the field change sinu-
soidally and consider currentflow and skin effect and theproblemreally gets
difficult. The ideas are important, but the exact answer is not worth worrying
about. Connecting wires and components to form circuits is standard prac-
tice. These conductors modify the fields around them. This is the same nasty
problem, and again it does not need an exact solution. What is needed is an
understanding of what actually takes place. Circuit theory does not consider
this type of problem.