CMOS Analog IC Design: Fundamentals

370 Pages·2017·19.7 MB·English

by  Erik Bruun

Downloaded from orbit.dtu.dk on: Oct 27, 2018

CMOS Analog IC Design: Fundamentals

Bruun, Erik

Pub lication date:
2018

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Citation (APA):
Bruun, E. (2018). CMOS Analog IC Design: Fundamentals. bookboon.
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ERIK BRUUN
CMOS ANALOG IC DESIGN
FUNDAMENTALS
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CMOS Analog IC Design: Fundamentals
1st edition
© 2018 Erik Bruun & bookboon.com
ISBN 978-87-403-2171-5
Peer review by Dr. Lars Stenberg, GN Hearing Danmark A/S
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CMOS ANALOG IC DESIGN: FUNDAMENTALS Contents
CONTENTS
Preface 7
Chapter 1 – Introduction 11
1.1 CMOS technology 11
1.2 Why analog circuit design? 12
1.3 Design methodology 14
References 16
Chapter 2 – Basic Concepts 17
2.1 Signals 17
2.2 Circuit elements 23
2.3 Circuit theorems 29
2.4 Circuit analysis 37
References 45
Problems 46
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CMOS ANALOG IC DESIGN: FUNDAMENTALS Contents
Chapter 3 – The MOS Transistor 49
3.1 Fundamentals of pn diodes 49
3.2 Physical characteristics of the MOS transistor 53
3.3 Electrical characteristics of the MOS transistor 56
3.4 Examples of the use of the Shichman-Hodges transistor model 68
3.5 Small-signal models 77
3.6 Deriving a small-signal equivalent circuit from a large-signal schematic 96
3.7 Advanced transistor models 103
References 108
Problems 110
Chapter 4 – Basic Gain Stages 115
4.1 The common-source stage at low frequencies 116
4.2 The common-drain stage at low frequencies 124
4.3 The common-gate stage and the cascode stage at low frequencies 133
4.4 The differential pair at low frequencies 146
4.5 Frequency response of the basic gain stages 171
References 193
Problems 194
Chapter 5 – Multistage Amplifiers 205
5.1 Cascode opamps 207
5.2 The two-stage opamp 209
5.3 The two-stage opamp with feedback 214
References 220
Problems 221
Chapter 6 – Feedback 225
6.1 The basic feedback structure 225
6.2 Advantages of feedback 226
6.3 Feedback topologies 237
6.4 The inverting amplifier 241
6.5 Stability 246
6.6 Frequency compensation 263
References 273
Problems 274
Chapter 7 – The Two-Stage Opamp 279
7.1 Specifications for a design example 280
7.2 Bandwidth and stability requirements 282
7.3 Bias point and transistor dimensions 288
7.4 Design verification and iteration 292
References 297
Problems 298
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CMOS ANALOG IC DESIGN: FUNDAMENTALS Contents
Chapter 8 – Bias Circuits, Bandgap References
and Voltage Regulators 301
8.1 Current mirrors 301
8.2 Bias current circuits with reduced supply voltage dependency 306
8.3 Bandgap voltage references 313
8.4 Voltage regulators 323
References 331
Problems 332
Chapter 9 – Essential Results and Equations 339
9.1 Design methodology 339
9.2 Circuit analysis 340
9.3 Device models, linear passive devices 341
9.4 Device model, pn diode 341
9.5 Small-signal models 341
9.6 Device models, MOS transistors 342
9.7 Basic gain stages at low frequency 346
9.8 Frequency response of basic gain stages 352
9.9 Feedback 354
9.10 The two-stage opamp 357
9.11 Current mirrors and current sources 359
9.12 Bandgap reference principle 360
9.13 Voltage regulators 361
Appendix – Answers to End-of-Chapter Problems 363
Index 368
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CMOSAnalogICDesign: Fundamentals Preface
CMOS ANALOG IC DESIGN: FUNDAMENTALS PrefaCe
Preface
ThisbookhasbeenwrittenwiththespecificgoaltoserveasatextbookforafirstcourseinCMOSanalog
integrated circuit design. It is intended for electronics engineering students at bachelor level who have
followedbasiccoursesinmathematics,physics,circuittheory,electronicsandsignalprocessing.
A distinct feature of this book is the emphasis on the interaction between analytical methods and simu-
lation methods. Traditionally, the teaching of circuit design is based on mathematical models of circuit
elements and on basic circuit theorems. Often, simulations are just referred to as additional examples.
Inthisbook,simulationsusingtheuniversallyacceptedprogramSPICE(SimulationProgramwithInte-
gratedCircuitEmphasis)areusedthroughout. Thesimulationsareintegratedintothetext,bothinorder
toillustrateandverifythemathematicallybasedtheoryandinordertodevelopdesignmethodsusingthe
simulatorformoreaccuratedesignofintegratedcircuits.
The material presented in this book has been adapted from material used by the author for many years
of teaching an introductory one-semester course (5 ECTS credits) in CMOS analog integrated circuit
designattheTechnicalUniversityofDenmark.
Chapter1isanintroductiontothesubject, outliningthebasicmethodforintegratedcircuitdesignwith
closeinteractionbetweenhandcalculationsandsimulations,andprovidingamotivationforthestudyof
analogintegratedcircuitdesign.
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CMOSAnalogICDesign: Fundamentals Preface
CMOS ANALOG IC DESIGN: FUNDAMENTALS PrefaCe
Chapter 2 is a recapitulation of some of the basic theory which you are expected to know already. This
recapitulationisusedforsettingthesceneforthefollowingchapterswhicharethebulkofthecourse.
Chapter 3 presents the models used for MOS transistors in the book. For analytical purposes, hand
calculations, the Shichman-Hodges model is used. For simulations, both the Shichman-Hodges model
andBSIMtransistormodelsarepresented.
Chapter 4 describes the basic gain stages in analog CMOS design, i.e., the common-source stage, the
common-drainstage,thecommon-gatestageandthedifferentialpair. Athoroughreviewoftheconcept
of small-signal analysis is given with several examples showing how to build a small-signal model of a
gainstagefromthetransistorschematicofthestage.
Chapter5isaboutmultistageamplifiers. Itisshownhowasimpleopampcanbedesignedbycombining
thestagesintroducedinchapter3.
Chapter6isabriefreviewoffeedbacktheory. Theuseoffeedbacktoimprovemanysystemparameters
in an amplifier is explained. Additionally, conditions for stability in a feedback system are presented.
Thechapterisalsoincludedinordertobeabletopresentadesignofthetwo-stageopamp,considering
that the main application of an opamp is as a gain element in a feedback system where the stability of
thesystemisacriticalparameter.
Chapter 7 reviews the two-stage opamp and presents a design where the issue of stability in a feedback
systemisamajorconsideration.
Chapter 8 gives a brief presentation of some circuits used for biasing of the amplifier circuits presented
inthepreviouschapter.
Finally, Chapter9summarizestheessentialsfromthepreviouschapters. Itisintendedasaquickrefer-
encetothemostimportantequationsandconclusionsfromthebook.
Allchapters(exceptChapter1andChapter9)includeend-of-chapterproblems,andanswerstotheques-
tionsareincludedinanAppendix. Thepracticalexperienceobtainedbysolvingasubstantialnumberof
problemsisessentialforthelearningprocessinafieldsuchasintegratedcircuitdesign.
The material presented in the book has been found suitable for a course comprising 12 lectures (with
problem solving sessions) and (optionally) an additional final wrap-up lecture. The duration of each
lectureisabout2hoursincludinga15minutesbreak.
Thelecturesmaybeorganizedasfollows:
Lecture1: Introductionandrecapitulationofbasictheory(Chapters1and2).
Lecture2: MOStransistorbasics,Shichman-Hodgestransistormodel(Chapter3.1–3.4).
Lecture3: Small-signaltransistormodelsandadvancedtransistormodels(Chapter3.5–3.7).
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CMOSAnalogICDesign: Fundamentals Preface
CMOS ANALOG IC DESIGN: FUNDAMENTALS PrefaCe
Lecture4: Common-sourcestageandcommon-drainstageatlowfrequencies(Chapter4.1–4.2).
Lecture5: Common-gatestageandcascodestageatlowfrequencies(Chapter4.3).
Lecture6: Thedifferentialgainstage(Chapter4.4).
Lecture7: Frequencyresponseofthebasicgainstages(Chapter4.5).
Lecture8: Introductiontomultistageamplifies(Chapter5).
Lecture9: Feedbacktheory,basicpropertiesofsystemswithfeedback(Chapter6.1–6.4).
Lecture10: Stabilityinfeedbacksystems(Chapter6.5–6.6).
Lecture11: Two-stageopampdesignexample(Chapter7).
Lecture12: Biasingcircuits(Chapter8).
Prerequisites: This book is aimed at a fundamental level in analog CMOS circuit design. The pre-
requisites needed are only a general background in mathematics and physics and a background in the
fundamentalsofsignalprocessing,circuittheoryandelectronics. Therearenumerouscoursesandtext-
books which will provide an adequate background. Without this being an exhaustive list, it can be
mentionedthatthetextbooksusedintheintroductorycoursesattheTechnicalUniversityofDenmarkin
signalprocessing,circuittheoryandelectronicsarethefollowing:
Lathi, BP. 2009, Signal Processing & Linear Systems, International Second Edition, Oxford University
Press,NewYork,USA.
Hambley, AR. 2014, Electrical Engineering, Principles and Applications, Sixth Edition, Pearson Edu-
cationLtd.,Harlow,UK.
Asalreadymentioned,animportantfeatureofthepresentbookistheextensiveuseofSPICEforverifica-
tionofthemathematicallybasedtheoryandforprovidingdesignswithpropertieswhichareclosertothe
propertiesobtainedthroughactualexperimentalcircuits. AveryusefulbookforlearningaboutLTspice
(the version of SPICE used in this book) is the following, part of which is also used in an introductory
courseincircuittheoryandelectronics:
Bruun,E.2017,CMOSIntegratedCircuitSimulationwithLTspice,SecondEdition,bookboon.
Availablefrom: http://bookboon.com/en/cmos-integrated-circuit-simulation-with-ltspice-ebook
If you are not already familiar with LTspice, it is highly recommended to complete Tutorials 1 and 2
fromthisbookconcurrentlywithreadingChapter2inthepresentbook.
Furtherreading: Hopefully,somereadersofthepresentbookfindthesubjectofCMOSanaloginte-
gratedcircuitdesignsointerestingthattheywishtostudythesubjectfurther. Therearemanyexcellent
textbooksaboutanalogCMOSdesigncoveringboththetopicsfromthepresentbookinmoredepthand
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