Dynamic offset compensated CMOS amplifiers

178 Pages·2009·8.62 MB·English

by  Dr Johan F. Witte

Dynamic Offset Compensated CMOS Amplifiers
ANALOG CIRCUITS AND SIGNAL PROCESSING SERIES
Consulting Editor: Mohammed Ismail. Ohio State University
For other titles published in this series, go to
www.springer.com/series/7381
Dynamic Offset Compensated
CMOS Amplifiers
Johan F. Witte, Kofi A.A. Makinwa, Johan H. Huijsing
Delft University of Technology, the Netherlands
Springer
Boston/Dordrecht/London
Dr. Johan F. Witte Prof. Kofi A.A. Makinwa
Delft University of Technology Delft University of Technology
Dept. Electrical Engineering Dept. Electrical Engineering
Mekelweg 4 Mekelweg 4
2628 CD Delft 2628 CD Delft
Netherlands Netherlands
[email protected] [email protected]
Prof. Johan H. Huijsing
Delft University of Technology
Dept. Electrical Engineering
Mekelweg 4
2628 CD Delft
Netherlands
[email protected]
ISBN 978-90-481-2755-9 e-ISBN 978-90-481-2756-6
DOI 10.1007/978-90-481-2756-6
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: 2009926941
©Springer Science+Business Media B.V. 2009
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Springer is part of Springer Science+Business Media (www.springer.com)
Preface
................................................................................................... ix
Acknowledgements
....................................................................... xi
1. Introduction
......................................................................................... 1
1.1 Motivation .............................................................................................. 1
1.2 Offset ...................................................................................................... 3
1.2.1Drain current mismatch ................................................................. 4
1.2.2Folded cascode amplifier offset ..................................................... 5
1.2.3Minimizing offset .......................................................................... 6
1.3 Challenges .............................................................................................. 7
1.4 Organisation of the book ........................................................................ 8
1.5 References ............................................................................................ 10
2. Dynamic Offset Compensation Techniques
............... 13
2.1 Introduction .......................................................................................... 13
2.2 Auto-zero amplifiers ............................................................................. 14
2.2.1Output offset storage ................................................................... 14
2.2.2Input offset storage ...................................................................... 16
2.2.3Auxiliary amplifier ...................................................................... 17
2.2.4Noise in auto-zero amplifiers ...................................................... 19
2.3 Chopper amplifiers ............................................................................... 23
2.3.1Noise in chopper amplifiers ......................................................... 25
2.3.2Chopped operational amplifier in a feedback network ................ 26
2.3.3Charge injection effects in chopper amplifiers ............................ 27
2.4 Chopped auto-zeroed amplifier ............................................................ 29
2.5 Switching non-idealities ....................................................................... 31
2.5.1Charge injection reduction tactics ............................................... 33
2.5.2Charge injection suppression circuits .......................................... 36
2.6 Conclusions .......................................................................................... 40
2.7 References ............................................................................................ 40
v
3. Dynamic Offset Compensated Operational
Amplifiers
..............................................................................................................43
3.1 Introduction .......................................................................................... 43
3.2 Ping-pong operational amplifier .......................................................... 44
3.3 Offset-stabilized amplifiers .................................................................. 45
3.3.1Auto-zero offset-stabilized amplifiers ......................................... 47
3.3.2Chopper offset-stabilized amplifiers ........................................... 48
3.3.3Frequency compensation ............................................................. 50
3.3.4Chopper stabilized amplifiers with ripple filters ......................... 55
3.3.5Chopper and auto-zero stabilized amplifiers ............................... 58
3.4 Chopper offset-stabilized chopper amplifiers ...................................... 59
3.4.1Iterative offset-stabilization ........................................................ 61
3.5 Conclusions .......................................................................................... 63
3.6 References ............................................................................................ 64
4. Dynamic Offset Compensated Instrumentation
Amplifiers
..............................................................................................................67
4.1 Introduction .......................................................................................... 67
4.1.1Current-feedback instrumentation amplifiers ............................. 69
4.2 Dynamic offset compensated instrumentation amplifiers .................... 74
4.2.1Chopper instrumentation amplifier ............................................. 75
4.2.2Auto-zeroed instrumentation amplifier ....................................... 76
4.2.3Ping-pong instrumentation amplifier .......................................... 78
4.2.4Ping-pong-pang instrumentation amplifier ................................. 78
4.2.5Offset-stabilized instrumentation amplifiers ............................... 79
4.2.6Chopper offset-stabilized chopper instrumentation amplifier ..... 82
4.3 Conclusions .......................................................................................... 82
4.4 References ............................................................................................ 82
vi
5. Realizations of Operational Amplifiers
........................ 85
5.1 Introduction .......................................................................................... 85
5.2 Chopper offset-stabilized operational amplifier ................................... 86
5.2.1Topology ...................................................................................... 86
5.2.2Circuits ........................................................................................ 91
5.2.3Measurement results .................................................................... 98
5.3 Chopper and auto-zero offset-stabilized operational amplifier .......... 104
5.3.1Topology .................................................................................... 104
5.3.2Circuits ...................................................................................... 107
5.3.3Measurement results .................................................................. 112
5.4 Conclusions ........................................................................................ 115
5.5 References .......................................................................................... 116
6. Realizations of Instrumentation Amplifiers
............ 117
6.1 Introduction ........................................................................................ 117
6.2 Low-offset indirect current-feedback instrumentation amplifier ....... 118
6.2.1Introduction ............................................................................... 118
6.2.2Topology .................................................................................... 118
6.2.3Circuits ...................................................................................... 122
6.2.4Measurement results .................................................................. 124
6.3 High-side current-sense amplifier ...................................................... 129
6.3.1Current-sensing .......................................................................... 129
6.3.2Topology .................................................................................... 133
6.3.3Circuits ...................................................................................... 138
6.3.4Measurement results .................................................................. 143
6.4 Conclusions ........................................................................................ 147
6.5 References .......................................................................................... 149
7. Conclusions and Future Directions
................................ 151
7.1 Conclusions ........................................................................................ 151
7.2 Future directions ................................................................................. 151
7.3 References .......................................................................................... 153
vii
A. Layout Issues
................................................................................... 155
A.1Introduction ......................................................................................... 155
A.2Chopper layout .................................................................................... 157
A.3Clock shielding .................................................................................... 160
A.4Conclusion ........................................................................................... 162
A.5References ........................................................................................... 162
About the Authors
....................................................................... 163
Index
...................................................................................................... 167
viii
Preface
CMOS amplifiers suffer from relatively poor offset specifications. Since the
1980s techniques have been explored to calibrate for this offset, or to let the
amplifier itself compensate for its offset in some way or another. This latter
approach is often done dynamically during operation of the amplifier, hence
the name “dynamic offset compensation”. This thesis describes the theory,
design and realization of dynamic offset compensated CMOS amplifiers.
Itfocuses on the design of general-purpose broadband operational amplifiers
and instrumentation amplifiers.
Two distinguishable offset compensation techniques are described in
chapter 2: auto-zeroing and chopping. Several topologies are discussed, in chapter
3 which can be used to design broadband dynamic offset-compensated
operational amplifiers as well as instrumentation amplifiers, which are described
in chapter 4. Four implementations are discussed in this book: two low-offset
broadband operational amplifiers in chapter 5, and chapter 6 discusses a
low-offset instrumentation amplifier, and a low-offset current-sense amplifier,
which can sense battery currents at a 28V rail.
J.F. Witte
K.A.A. Makinwa
J.H. Huijsing
Delft, December 2008
ix