Table Of ContentAnalog Circuits and Signal Processing
Leila Safari
Giuseppe Ferri
Shahram Minaei
Vincenzo Stornelli
Current-Mode
Instrumentation
Amplifi ers
Analog Circuits and Signal Processing
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Leila Safari • Giuseppe Ferri • Shahram Minaei
Vincenzo Stornelli
Current-Mode
Instrumentation Amplifiers
Leila Safari Giuseppe Ferri
Tehran, Iran University of L’Aquila
L’aquila, Italy
Shahram Minaei
Doğuş University Vincenzo Stornelli
Istanbul, Turkey University of L’Aquila
L’aquila, Italy
ISSN 1872-082X ISSN 2197-1854 (electronic)
Analog Circuits and Signal Processing
ISBN 978-3-030-01342-4 ISBN 978-3-030-01343-1 (eBook)
https://doi.org/10.1007/978-3-030-01343-1
Library of Congress Control Number: 2018957333
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Preface
Instrumentation amplifiers (IAs) are among the oldest and most widely used circuits
that ensure a weak differential signal amplification in the presence of strong noises
and common-mode signals. In the past, IAs were implemented using Op-Amps and
resistors. Their major problem is the strict matching requirement between resistors
to achieve a high common-mode rejection ratio (CMRR). Another limitation associ-
ated with Op-Amp-based IAs is their gain-dependent bandwidth. These weaknesses
along with the rapid downscale of CMOS technology with reduced allowed supply
voltages have made the Op-Amp-based IAs less attractive. Fortunately, after the
emergence of current-mode signal processing, designers took the advantages of
current-mode technique to mitigate the problems associated with Op-Amp-based
IAs. Compared to conventional voltage-mode signal processing, the new technique
showed interesting features such as wide frequency performance, simpler circuitry,
low-voltage operation. This new generation of IAs based on current-mode signal
processing is known as current-mode instrumentation amplifiers (CMIAs). Although
signal processing is performed in current domain, the input and output signals in
CMIAs can be current or voltage signals. Therefore, while benefiting from inherent
advantages of current-mode signal processing such as low-voltage operation, high-
frequency performance, simpler circuitry, CMIAs can cover a wide range of appli-
cations. The first CMIA was reported in 1989 by C. Toumazou and F. J. Lidgey,
based on supply current sensing technique. This new CMIA utilized two Op-Amps
and one resistor. It showed interesting features such as high CMRR without requir-
ing tightly matched resistors and wide bandwidth independent of gain. Later, the
famous Wheatstone bridge was also employed and modified to take advantage of
current-mode signal processing. The current-mode Wheatstone bridge (CMWB)
and mixed-mode Wheatstone bridge were introduced, being capable of operating
with current-mode readout circuits. These advances provided the opportunity for
nearly all types of sensor readout circuits to benefit from current-mode signal pro-
cessing. Then, the CMIAs emerged as a rapidly advancing subject, so numerous
topologies are found in literature, and new current-mode building blocks were intro-
duced intended for CMIA applications. However, a book entirely and exclusively
dedicated to the design of CMIAs is lacking. We decided to write this book to
v
vi Preface
address the need for a guide on CMIA design and applications. It grew out employ-
ing the content of published journal and conference papers in the CMIA subject
written by researchers all around the world. Our aim is to give an overall knowledge
on CMIA design and make the comparison between various structures easier. The
operation principle, advantages, and disadvantages of each topology are high-
lighted. Also, we have classified the reported CMIAs in four categories depending
on their input and output signals. This classification simplifies selecting a specific
topology for the desired application.
This book is written in nine chapters.
In the first chapter, the general definitions of the common-mode rejection ratio
concept in single-ended, fully differential, and cascaded structures are studied.
Then, we discuss about the limitations of the conventional Op-Amp-based IAs. The
general classification of CMIAs is also developed in this chapter.
In Chap. 2, we cover supply current sensing technique which is the oldest and
powerful method used in the design of CMIA. The basic concept and performance
analysis of circuits based on this technique are discussed. The first and second gen-
erations of CMIAs developed using this technique are reviewed. Then, performance
analysis of each generation as well as their limitations is studied. This chapter ends
with an interesting comparison between the two generations.
In Chap. 3, we discuss about the Wheatstone bridges. First the fundamentals of
conventional voltage-mode Wheatstone bridge (VMWB) and its readout circuits are
studied. Then current-mode Wheatstone bridge (CMWB) principle, its readout cir-
cuit, and linearization technique are discussed. At the end of this chapter, the mixed-
mode Wheatstone bridge principle and readout circuits which are aimed to take the
benefits of both voltage-mode and current-mode signal processing are covered.
In Chap. 4, we consider the CMIA topologies designed with current conveyors.
As the second-generation current conveyor (CCII) is considered the most famous
and widely used current-mode building block, a chapter is solely dedicated to the
CCII-based CMIA topologies. These CMIAs include topologies proposed by
Wilson, Gift, Khan et al., Galanis and Haritantis, Su and Lidgey, Gkotsis et al., Koli
and Halonen, etc. The principles and the effect of CCII’s non-idealities on the over-
all CMRR of each topology are also studied.
In Chap. 5, all CMIA topologies based on various current-mode building blocks
are described. These building blocks include operational floating current conveyor
(OFCC), current differencing buffered amplifier (CDBA), current feedback opera-
tional amplifier (CFOA), operational transresistance amplifier (OTRA), differential
difference current conveyor (DDCC), and differential voltage current conveyor
(DVCC). The CMIAs studied in this chapter are classified according to their input
and output signals.
In Chap. 6, we study CMIA structures with electronically tunable gain feature.
Different methods used to achieve electronically tunable gain are discussed. The
electronically tunable CMIAs are divided into two groups. In first group, gain is
varied by the active building block, while, in second group, electronically variable
resistors are used for this purpose.
Preface vii
In Chap. 7, we briefly discuss about the implications (and limitations) caused by
mismatches in the CMIAs. Helpful techniques used to reduce the occurrence of
mismatches are also reviewed. The chapter is finished by studying a CMIA topol-
ogy with robust performance against mismatches.
In Chap. 8, we focus on the CMIAs designed for biomedical and low-voltage
low-power applications. In particular, design considerations and challenges for bio-
medical applications are discussed. We study the realization of well-known boot-
strapping technique in current-mode domain. Techniques used to improve noise
performance of CMIAs are also reviewed. Then, various methods and implementa-
tions used to design low-voltage low-power CMIAs are studied.
In the final chapter, the CMIAs intended for sensor applications are reviewed.
These include piezo-resistive, differential capacitive, ISFET, pH, and temperature
sensors. For each application, background knowledge on the related sensor is given,
and then the topology of the used CMIA is studied.
The intended audience for this book includes design engineers, researchers, and
students. We tried our best to present each chapter in the simplest form as possible
and independent of other chapters, so the readers are able to select and read a single
chapter separately, based on their requirement.
We hope that this book will be helpful in inspiring new ideas in CMIA design
and applications.
Tehran, Iran Leila Safari
L’aquila, Italy Giuseppe Ferri
Istanbul, Turkey Shahram Minaei
L’aquila, Italy Vincenzo Stornelli
Contents
1 Principles of Instrumentation Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Principles and Applications of Instrumentation Amplifiers . . . . . . . . 1
1.2 Common-Mode Rejection Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 Definitions of Common-Mode Rejection Ratio . . . . . . . . . . . 3
1.2.2 Common-Mode Rejection Ratio for Cascaded Stages. . . . . . 5
1.3 Conventional 3-Op-Amp Based Voltage-Mode Instrumentation
Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 CMRR Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.2 Differential Gain Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.3 Gain Bandwidth Conflict . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4 Current-Mode Instrumentation Amplifiers (CMIAs) . . . . . . . . . . . . . 11
1.4.1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4.2 Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 CMIA Based on Op-Amp Power Supply Current
Sensing Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1 Op-Amp Power Supply Current Sensing Technique . . . . . . . . . . . . . 15
2.1.1 Basic Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.2 Analysis of Op-Amp Power Supply Current
Sensing Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.1.3 Limitation and Design Challenges . . . . . . . . . . . . . . . . . . . . . 18
2.2 CMIA Based on Op-Amp Power Supply Current Sensing . . . . . . . . 19
2.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2.2 First Generation with Single-Output Structure . . . . . . . . . . . 20
2.2.3 Second Generation with Balanced Structure . . . . . . . . . . . . . 23
2.2.4 Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.2.5 Comparison Between Different Generations of CMIA
Based on Op-Amp Power Supply Sensing Technique . . . . . . 27
2.3 C onclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
ix
x Contents
3 Current-Mode Wheatstone Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.1 Traditional Voltage-Mode Wheatstone Bridge . . . . . . . . . . . . . . . . . . 29
3.1.1 Introduction to Traditional Voltage-Mode
Wheatstone Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.1.2 Read-Out Circuits for Voltage-Mode Wheatstone Bridge . . . 32
3.1.3 Linearization of Voltage-Mode Wheatstone Bridge . . . . . . . . 35
3.2 C urrent-Mode Wheatstone Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.1 Introduction to Current-Mode Wheatstone Bridge . . . . . . . . 36
3.2.2 Linearization of Current-Mode Wheatstone Bridge . . . . . . . 39
3.2.3 Read-Out Circuits for Current-Mode Wheatstone Bridge . . . 40
3.3 Mixed-Mode Wheatstone Bridge and Read-Out Circuits . . . . . . . . . 54
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4 Current-Mode Instrumentation Amplifiers
Using Current Conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.1 CCII-Based Basic CMIAs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.1.1 Wilson Current-Mode Instrumentation Amplifier . . . . . . . . . 59
4.1.2 Gift Current-Mode Instrumentation Amplifier. . . . . . . . . . . . 62
4.2 Current Conveyor-Based Enhanced CMIAs with Double
Common- Mode Cancellation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2.1 Khan et al. Current-Mode Instrumentation Amplifier . . . . . . 63
4.2.2 Su and Lidgey Current-Mode Instrumentation Amplifier . . . 64
4.2.3 Galanis Current-Mode Instrumentation Amplifier . . . . . . . . . 65
4.2.4 Gkotsis Current-Mode Instrumentation Amplifier . . . . . . . . . 66
4.2.5 Koli Current-Mode Instrumentation Amplifier . . . . . . . . . . . 66
4.2.6 Azhari and Fazlalipour Current-Mode
Instrumentation Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.2.7 Gift et al. Enhanced Current-Mode Instrumentation
Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5 Current-Mode Instrumentation Amplifiers Based
on Various Current- Mode Building Blocks . . . . . . . . . . . . . . . . . . . . . . 71
5.1 Current Input-Current Output (I-I) CMIAs . . . . . . . . . . . . . . . . . . . . 71
5.1.1 CDBA-Based I-I CMIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.1.2 CFOA Based I-I CMIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.1.3 OFCC-Based I-I CMIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.2 Current Input-Voltage Output (I-V) CMIAs . . . . . . . . . . . . . . . . . . . 77
5.2.1 OFCC-Based I-V CMIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.2.2 OTRA-Based I-V CMIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.3 Voltage Input-Current Output (V-I) CMIAs . . . . . . . . . . . . . . . . . . . 82
5.3.1 OFCC-Based CMIA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.4 Voltage Input-Voltage Output (V-V) CMIAs . . . . . . . . . . . . . . . . . . . 83
5.4.1 OFCC Based V-V CMIAs . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.4.2 DDCC-Based V-V CMIAs . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
