DESIGN OF LOW-VOLTAGE, LOW-POWER OPERATIONAL AMPLIFIER CELLS

Transcription

1 DESIGN OF LOW-VOLTAGE, LOW-POWER OPERATIONAL AMPLIFIER CELLS

2 THE KLUWER INTERNATIONAL SERIES IN ENGINEERING AND COMPUTER SCIENCE ANALOG CIRCUITS AND SIGNAL PROCESSING Consulting Editor Mohammed Ismail Ohio State University Related Titles: CHARACTERIZATION METHODS FOR SUBMICRONMOSFETs, editedby HishamHaddara ISBN: LOW-VOLTAGELOW-POWER ANALOG INTEGRATED CIRCUITS,edited by Wouter Serdijn ISBN: INTEGRATED VIDEO-FREQUENCY CONTINUOUS-TIME FILTERS: High-Performance Realizationsin BiCMOS, ScottD. Willingham, KenMartin ISBN: FEED-FORWARD NEURALNETWORKS: Vector Decomposition Analysis, Modelling andanalog Implementation, Anne-Johan Annema ISBN: FREQUENCY COMPENSATION TECHNIQUES LOW-POWER OPERATIONAL AMPLIFIERS, RuudEaschauzier, JohanHuijsing ISBN: ANALOG SIGNAL GENERATION FOR BIST OF MIXED-SIGNAL INTEGRATED CIRCUITS, Gordon W. Roberts, AlbertK. Lu ISBN: INTEGRATED FIBER-OPTIC RECEIVERS, AaronBuchwald, Kenneth W. Martin ISBN: MODELING WITH AN ANALOGHARDWAREDESCRIPTION LANGUAGE, H. AlanMantooth,MikeFiegenbaum ISBN: LOW-VOLTAGE CMOS OPERATIONAL AMPLIFIERS: Theory, Designand Implementation, SatoshiSakurai, Mohammed Ismail ISBN: ANALYSISANDSYNTHESISOF MOS TRANSLINEARCIRCUITS, Remco J. Wiegerink ISBN: COMPUTER-AIDED DESIGN OF ANALOG CIRCUITS AND SYSTEMS, 1. Richard Carley, Ronald S. Gyurcsik ISBN: HIGH-PERFORMANCE CMOS CONTINUOUS-TIME FILTERS, Jose Silva-Martinez, Michiel Steyaert, WillySansen ISBN: SYMBOLIC ANALYSIS OF ANALOG CIRCUITS: Techniques and Applications, Lawrence P. Huelsman, Georges G. E. Gielen ISBN: DESIGNOF LOW-VOLTAGE BIPOLAR OPERATIONAL AMPLIFIERS, M. JeroenFonderie, JohanH. Huijsing ISBN: STATISTICALMODELING FOR COMPUTER-AIDEDDESIGN OF MOS VLSI CIRCUITS, Christopher Michael, Mohammed Ismail ISBN: X SELECTIVE LINEAR-PHASESWITCHED-CAPACITOR AND DIGITAL FILTERS, Hussein Baher ISBN: ANALOG CMOS FILTERS FOR VERY HIGH FREQUENCIES, BramNauta ISBN: ANALOGVLSI NEURAL NETWORKS, Yoshiyasu Takefuji ISBN: ANALOGVLSI IMPLEMENTATION OF NEURALNETWORKS, CarverA. Mead, Mohammed Ismail ISBN: AN INTRODUCTION TO ANALOG VLSI DESIGN AUTOMATION, Mohammed Ismail, Jose Franca ISBN:

3 DESIGN OF LOW.VOLTAGE, LOW POWER OPERATIONAL AMPLIFIER CELLS by Ron Hogervorst and Johan H. Huijsing T.U. Delft, The Netherlands Springer-Science+Business Media, B.V.

4 A C.I.P. Catalogue record for this book is available from the Library of Congress ISBN ISBN (ebook) DOI / Printed on acid-free paper All Rights Reserved 1996 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in Softcover reprint of the hardcover 1st edition 1996 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner. Third Printing This printing is a digital duplication of the original edition.

5 Preface List of symbols ix xi 1 Introduction Low-voltage low-power CMOS circuits Design issues Organization of the work References 4 2 Low-Voltage Analog Design Considerations Introduction Classification of CMOS low-voltage circuits Electrical properties of MOS transistors Strong inversion Weak inversion ll Moderate inversion Rail-to-rail signals Rail-to-rail stages Conclusions References 17 3 Input Stages Introduction Single differential input stage Rail-to-rail input stage 27 3:4 Constant-g., rail~to-rail input stages Rail-to-rail input stages with current-based gm control Rail-to-rail input stages with voltage-based gm control., Rail-to-rail input stage with W over L based gm control Conclusions References 63 Low- Voltage Low-Power CMOS Operational Amplifier Cells v

6 4 Output Stages Introduction Common-source output stage Class-AB output stages Feedforward class-ab output stages Feedback class-ab output stage Conclusions References 86 5 Overall Topologies Introduction Single-stage amplifier Two-stage amplifiers Miller compensation Miller zero cancellation Cascoded Miller compensation Ito Nested cascoded Miller compensation Comparison offrequency compensation methods Three-stage amplifiers Nested Miller compensation Multipath nested Miller compensation Four-stage operational amplifiers Hybrid nested Miller compensation Multipath hybrid nested Miller compensation Conclusions References Realizations Introduction V compact operational amplifiers Topology of the compact opamp Input stage with gm control by three-times current mirrors Input stage with gm control by an electronic zener Input stage with gmcontrol by a one-time current mirror 172 vi Low- Voltage Low-Power CMOS Operational Amplifier Cells

7 6.2.5 Input stage with gm control by multiple input pairs Conclusions V operational amplifiers Overall designs Measurement results Conclusions Fully differential operational amplifiers V one-stage operational amplifier V two-stage operational amplifier V four-stage operational amplifier Conclusions References 203 INDEX 205 Low- Voltage Low-Power CMOS Operational Amplifier Cells vii

8 Preface This book addresses the design and realization of low-voltage low-power CMOS operational amplifier cells. It is the result of a Ph.D. project performed at the Delft University of Technology, The Netherlands. The book discusses all the circuit parts necessary to realize low-voltage lowpower CMOS operational amplifiers, such as constant-g., rail-to-rail input stages, c1ass-ab rail-to-rail output stages and frequency compensation methods. In addition, several silicon realizations are treated. The contents of this book will be of particular interest to professional designers and graduate students. The reader is presumed to have basic knowledge of analog integrated circuit design. In the first chapter of this book, the motivation behind this book is given. The question is answered why low-voltage low-power CMOS operational amplifiers are needed. Chapter 2 gives a classification of low-voltage circuits in terms of gate-source voltages and saturation voltages. Two groups of low-voltage circuits are distinguished: low-voltage and extremely low-voltage circuits. The first group requires a minimum supply voltage of two gate-source voltages and two saturation voltages. Typical values lie between 2 and 3 V. The second group requires a minimum supply voltage of one gate-source voltage and one saturation voltage. Typical values are between 1 and 2 V. Further some design considerations that are encountered in low-voltage design are described in this chapter. Chapter 3 addresses the design of input stages. The properties of a conventional input pair as well as the properties of a complementary railto-rail input stage are discussed. To obtain a power-optimal frequency compensation a rail-to-rail input stage should have a constant transconductance. To achieve this several rail-to-rail input stages having a constant transconductance are designed. Constant transconductance input stages which are able to operate in weak or strong inversion are described. Chapter 4 treats the design of low-voltagepower-efficientc1ass-ab output stages. Two classes of c1ass-ab control circuits are distinguished: feedforward and feedback control. The feedforward c1ass-ab control Low-Voltage Low-Power CMOS OperationalAmplifier Cells ix

9 circuits are able to operate on low supply voltages while the feedback control circuits are able to run under extremely low supply voltages. Chapter5 discusses overall topologies and frequency compensation techniques of operational amplifiers. The first section of this chapter is dedicated to the high-frequency performance of a one-stage amplifier. The next sections discuss several frequency compensation techniques for two, three, and four-stage operational amplifiers. Chapter 6 discusses the design and realization of several complete operat ional amplifiers. The amplifiers are constructed using the circuit parts described in the previous chapters. Six different implementations of a 3-V compact rail-to-rail two-stage operational amplifier are discussed. In addition two versions of a 1.5-V four-stage operational amplifier are discussed. At the end of this chapter three different operational amplifiers with a differential input and output are discussed. Ron Hogervorst Johan H. Huijsing Delft, July 12, 1996 x Low- Voltage Low-Power CMOS Operational Amplifier Cells

10 List ofsymbols Symbol Quantity Unit p transconductance factor AJV2 y bulk-threshold parameter IN I / 2 0 gate electric field parameter IN A,R bandwidth reduction factor Il charge carrier mobility cm 2Ns ~ source-drain electrical field parameter urn/v Ij>f flat-band voltage V 0- real part ofthe complex frequency rad/s co pole frequency radls CO u unity-gain frequency rad/s Ao DC open-loop gain db AT closed-loop voltage gain c gs gate-source capacitance F CMRR common-mode rejection ratio db C capacitor F C M Miller capacitor F C L load capacitor F Cox normalized oxide capacitance F/m 2 f frequency Hz gm transconductance.a-i go output conductance.a-i ld drain current A lpull pull current A lpush push current A Low-Voltage Low-Power CMOS Operational Amplifier Cells xi

11 I q quiescent current A Is specific current A jeo imaginary part of the complex frequency radls k Boltzmann's constant, JIK K f flicker noise component y2p L channel length m n weak inversion slope factor p pole radls rds drain-source resistance n R resistor.n R L load resistor n T absolute temperature K V 2 eq squared equivalent input noise voltage y2 IHz Vcommon common-mode input voltage Y V DD positive supply voltage Y V ds drain-source voltage Y V dsat saturation voltage Y V gs gate-source voltage Y Vgs. elf effective gate-source voltage Y Vos offset voltage Y V sb source-bulk voltage V Vss negative supply voltage V V sup supply voltage Y Vsup,min minimum supply voltage V V th thermal voltage Y V T threshold voltage V V TO threshold voltage at Vsb=OV V W channel width m z zero radls Z impedance n xii Low- Voltage Low-Power CMOS Operational Amplifier Cells