CMOS CURRENT AMPLIFIERS THE KLUWER INTERNATIONAL SERIES IN ENGINEERING AND COMPUTER SCIENCE ANALOG CIRCUITS AND SIGNAL PROCESSING Consulting Editor: Mohammed Ismail. Ohio State University Related Titles: DATA CONVERTERS FOR WIRELESS STANDARDS C. Shi and M. Ismail ISBN: 0-7923-7623-4 AUTOMATIC CALIBRATION OF MODULATED FREQUENCY SYNTHESIZERS D. McMahill ISBN: 0-7923-7589-0 MODEL ENGINEERING IN MIXED-SIGNAL CIRCUIT DESIGN S. Huss ISBN: 0-7923-7598-X CONTINUOUS-TIME SIGMA-DELTA MODULATION FOR A/D CONVERSION IN RADIO RECEIVERS L. Breems, J.H. Huijsing ISBN: 0-7923-7492-4 DIRECT DIGITAL SYNTHESIZERS: THEORY, DESIGN AND APPLICATIONS J. Vankka, K. Halonen ISBN: 0-7923 7366-9 SYSTEMATIC DESIGN FOR OPTIMISATION OF PIPELINED ADCs J. Goes, J.C. Vital, J. Franca ISBN: 0-7923-7291-3 OPERATIONAL AMPLIFIERS: Theory and Design J. Huijsing ISBN: 0-7923-7284-0 HIGH-PERFORMANCE HARMONIC OSCILLATORS AND BANDGAP REFERENCES A. van Staveren, C.J.M. Verhoeven, A.H.M. van Roermund ISBN: 0-7923-7283-2 HIGH SPEED A/D CONVERTERS: Understanding Data Converters Through SPICE A. Moscovici ISBN: 0-7923-7276-X ANALOG TEST SIGNAL GENERATION USING PERIODIC ENCODED DATA STREAMS B. Dufort, G.W. Roberts ISBN: 0-7923-7211-5 HIGH-ACCURACY CMOS SMART TEMPERATURE SENSORS A. Bakker, J. Huijsing ISBN: 0-7923-7217-4 DESIGN, SIMULATION AND APPLICATIONS OF INDUCTORS AND TRANSFORMERS FOR Si RF ICs A.M. Niknejad, R.G. Meyer ISBN: 0-7923-7986-1 SWITCHED-CURRENT SIGNAL PROCESSING AND A/D CONVERSION CIRCUITS: DESIGN AND IMPLEMENTATION B.E. Jonsson ISBN: 0-7923-7871-7 RESEARCH PERSPECTIVES ON DYNAMIC TRANSLINEAR AND LOG-DOMAIN CIRCUITS W.A. Serdijn, J. Mulder ISBN: 0-7923-7811-3 CMOS DATA CONVERTERS FOR COMMUNICATIONS M. Gustavsson, J. Wikner, N. Tan ISBN: 0-7923-7780-X DESIGN AND ANALYSIS OF INTEGRATOR-BASED LOG -DOMAIN FILTER CIRCUITS G.W. Roberts, V. W. Leung ISBN: 0-7923-8699-X VISION CHIPS A. Moini ISBN: 0-7923-8664-7 CMOS CURRENT AMPLIFIERS Speed versus Nonlinearity by Kimmo Koli Nokia Research Center, Finland and Kari Halonen Helsinki University of Technology, Finland KLUWER ACADEMIC PUBLISHERS NEW YORK,BOSTON, DORDRECHT, LONDON, MOSCOW eBookISBN: 0-306-48003-4 Print ISBN: 1-4020-7045-4 ©2003 Kluwer Academic Publishers NewYork, Boston, Dordrecht, London, Moscow Print ©2002 Kluwer Academic Publishers Dordrecht All rights reserved No part of this eBook maybe reproducedor transmitted inanyform or byanymeans,electronic, mechanical, recording, or otherwise, without written consent from the Publisher Created in the United States of America Visit Kluwer Online at: http://kluweronline.com and Kluwer's eBookstore at: http://ebooks.kluweronline.com Contents 1 Introduction to current-mode circuit techniques 1 1.1 Development of integration technologies 1 1.2 Motivation for current-mode circuit design 2 1.3 Evolution of current-mode building blocks 3 1.4 Adjoint principle 4 1.5 Scope of this book 6 2 Basic current amplifiers 11 2.1 Current-mirror 12 2.1.1 Nonidealities due to the channel length modulation 13 2.1.2 Nonidealities due the mismatch 16 2.1.3 High frequency nonidealities 18 Linear effects 18 Nonlinearity in limited frequency ranges 20 Mirror as a feedback amplifier 22 2.1.4 Distortion reduction methods 27 Transconductance linearisation 27 Nonlinear current reduction 28 Nonlinear current cancellation 28 2.1.5 Noise and dynamic range 31 2.1.6 Other mirror topologies 33 Accurate current-mirror topologies for large signal amplitudes 33 Resistively compensated mirror 35 2.2 Current buffer 38 2.2.1 Linear nonidealities 39 2.2.2 Nonlinearity 40 2.2.3 Noise 41 2.2.4 Alternative topologies 41 vi Contents 3 Open-loop current amplifiers 45 3.1 First generation current-conveyor CCI 45 3.1.1 Linear nonidealities 46 3.1.2 Nonlinearity 49 3.1.3 Applications of the CCI 49 3.1.4 Push-pull CCI topologies 50 3.1.5 Low voltage CCI topologies 54 3.2 Second generation current-conveyor CCII 55 3.2.1 Linear nonidealities 57 3.2.2 CCII macromodel 59 3.2.3 Applications of the CCII 61 3.2.4 Nonlinearity of the class-A CCII 67 3.2.5 Alternative class-A CCII topologies 68 3.2.6 Push-pull CCII topologies 72 Basic operation of a push-pull CCII+ 72 Basic operation of a push-pull CCII- 74 X-terminal impedance 75 Current gain nonlinearity 76 3.3 Third generation current-conveyor CCIII 80 4 Current-mode feedback amplifiers 85 4.1 Current-feedback operational amplifier 85 4.1.1 Closed loop bandwidth 87 4.1.2 Integrator implementations 90 4.1.3 Self-compensation of voltage followers 92 4.1.4 Common-mode rejection 93 4.1.5 CMOS implementations 95 4.2 Operational floating conveyor 97 4.2.1 Applications 98 4.2.2 Composite conveyors 99 4.3 Current-mode operational amplifiers 101 4.3.1 Distortion 102 4.3.2 Slew rate and full power bandwidth 104 4.3.3 Alternative topologies 105 4.4 High-gain current-conveyor 107 4.4.1 Linear nonidealities 108 4.4.2 Applications 110 4.4.3 Distortion 113 4.4.4 Design example 115 Contents vii 5 System aspects of current-mode circuits 123 5.1 Input voltage-to-current conversion 123 5.2 Output current-to-voltage conversion 126 5.3 Differential voltage input structures 129 5.3.1 CMRR enhancement techniques 130 Common-mode bootstrapping 131 Output current subtraction 131 Composite conveyors 135 5.4 Differential current input structures 137 5.5 Single-ended to differential conversion 138 5.6 Noise in current-mode circuits 141 5.6.1 Class-A CMOS CCII+ 141 5.6.2 Other low-gain conveyor topologies 145 5.6.3 High-gain current-conveyor 145 5.6.4 Other current-mode feedback amplifiers 148 5.6.5 General notes on current amplifier noise 149 6 Current-mode continuous-time filters 153 6.1 Integrator quality factor 154 6.2 Voltage-mode active-RC integrators 155 6.3 OTA-based integrators 157 6.3.1 The effects of process variation and temperature drift 158 6.3.2 Transconductance linearity 160 6.4 Integrators with MOS-resistors 162 6.5 Current-conveyor based filters 163 6.6 Current-mirror based filter 167 6.7 High-gain current-conveyor based filters 172 6.8 Multi-output current integrator with a linearised transconductor 176 6.8.1 Linearization by drain current difference 177 6.8.2 Linearisation by dynamic biasing 181 6.9 Design case: A 1 MHz current-mode low-pass filter 183 6.9.1 Filter building blocks 183 The transimpedance driver amplifier 184 Multiple-output linearised transconductance element 187 Temperature drift compensation of the integrator time constant 187 6.9.2 The first filter realisation 190 Integrator Q-enhancement 192 Experimental results 195 6.9.3 The second test chip 198 viii Contents Alternate driver implementation 201 Experimental results 205 6.10 Final remarks 208 7 Current-mode logarithmic amplifiers 213 7.1 Diode-feedback logarithmic amplifiers 214 7.1.1 Voltage-mode operational amplifier based realizations 214 7.1.2 Design case: based logarithmic peak detector 216 BiCMOS implementation of a 217 Logarithmic peak detector implementation 217 Post processing of the logarithmic output voltage 222 Final remarks on the design 229 7.2 Pseudologarithmic amplifiers 230 7.2.1 Limiting CMOS voltage amplifiers 231 7.2.2 Limiting CMOS current amplifiers 233 7.2.3 Accuracy of the pseudologarithmic amplifier 235 7.2.4 Amplitude detection in pseudologarithmic amplifiers 236 CMOS rectifiers 236 CMOS squarers 238 CMOS peak detectors 238 7.2.5 Design case: A 2.5 V CMOS pseudologarithmic current am- plifier 242 Limiting amplifier 243 Current reference 245 Current peak detector 247 Experimental results 247 7.3 Other approaches 252 Current peak detector with enhanced discharging time con- stant adjustment 252 Conclusions 259 A Basic distortion definitions 261 A.1 Harmonic distortion 261 A.2 Intermodulation distortion 262 A.3 Distortion in feedback amplifiers 263 A.3.1 Distortion in quasi-static feedback amplifiers 263 A.3.2 Distortion in dynamic feedback amplifiers 264 Contents ix B Distortion in push-pull current amplifiers 269 B.1 Class-A operation 269 B.2 Class-AB operation 271 C Distortion in CMOS operational amplifiers 275 C.1 Miller-compensated unbuffered operational amplifier 275 C.2 Folded cascode operational transconductance amplifier 279 D Distortion in a dual current-mirror integrator 283 D.1 Single-ended integrator 283 D.2 Differential integrator 286