Biopotential readout circuits for portable acquisition systems

Biopotential Readout Circuits for Portable Acquisition Systems describes one of the main building blocks of such miniaturized biomedical signal acquisition systems. The focus of this book is on the implementation of low-power and high-performance integrated circuit building blocks that can be used to extract biopotential signals from conventional biopotential electrodes. New instrumentation amplifier architectures are introduced and their design is described in detail. These amplifiers are used to implement complete acquisition demonstrator systems that are a stepping stone towards practical miniaturized and low-power systems.

1 Introduction	p. 1
1.1 Ambulatory Health Care Systems	p. 1
1.2 Body Area Networks	p. 1
1.3 Scope of the Book	p. 2
2 Introduction to Biopotential Acquisition	p. 5
2.1 Introduction	p. 5
2.2 Introduction to Biopotential Signals	p. 5
2.3 Introduction to Biopotential Electrodes	p. 6
2.3.1 Equivalent Circuit Model	p. 7
2.3.2 Types of Biopotential Electrodes	p. 8
2.4 Introduction to Biopotential Amplifiers	p. 9
2.4.1 Interference Theory	p. 10
2.4.2 Noise-Efficiency Factor (NEF) of Biopotential Amplifiers	p. 11
2.4.3 State-of-the-Art in Instrumentation Amplifier Design	p. 12
2.5 Introduction to Chopper Modulation Technique	p. 13
2.5.1 Noise Analysis of Chopper Modulation Technique	p. 14
2.5.2 Charge Injection and Residual Offset of Chopper Modulated Amplifiers	p. 15
2.5.3 Signal Distortion in Chopper Modulated Amplifiers	p. 17
2.5.4 CMRR of the Chopper Modulated Amplifiers	p. 18
2.6 Conclusions	p. 18
3 24-Channel EEG Readout Front-End ASIC	p. 21
3.1 Introduction	p. 21
3.2 ASIC Architecture	p. 21
3.3 Current Balancing IA	p. 22
3.3.1 Implementation	p. 22
3.3.2 Measurement of Performance	p. 24
3.4 CMRR Model for Biopotential Instrumentation Amplifiers	p. 25
3.4.1 Systematic CMRR	p. 26
3.4.2 CMRR Limit Due to Differential DC Electrode Offset	p. 28
3.4.3 Verification of the CMRR Model	p. 29
3.5 Programmable Gain Stage	p. 30
3.5.1 Finite-Gain Compensated SC Amplifier	p. 30
3.5.2 Programmable Gain Stage Implementation	p. 32
3.6 Test Results	p. 34
3.7 Conclusions	p. 36
4 Biopotential Readout Front-End ASICs	p. 39
4.1 Introduction	p. 39
4.2 AC Coupled Chopper Modulated IA (ACCIA)	p. 40
4.2.1 Architecture of the ACCIA	p. 40
4.2.2 Architecture of the CBIA	p. 44
4.2.3 Power-Noise Performance of the ACCIA	p. 48
4.3 Chopping Spike Filter (CSF)	p. 50
4.4 Low-Power Programmable Gain Stage	p. 51
4.5 Single-Channel ExG Readout Front-End	p. 53
4.5.1 Implementation	p. 53
4.5.2 Measurement of Performance	p. 56
4.5.3 Biological Test Results	p. 61
4.6 Eight-Channel EEG Readout Front-End	p. 63
4.6.1 Implementation	p. 63
4.6.2 Measurement of Performance	p. 68
4.6.3 Biological Test Results	p. 71
4.7 Comparison with the State-of-the-Art	p. 75
4.8 Conclusions	p. 77
5 A Complete Biopotential Acquisition ASIC	p. 79
5.1 Introduction	p. 79
5.2 ASIC Architecture	p. 79
5.3 Bias Generator Circuit	p. 81
5.4 Class-AB Buffer Architecture	p. 85
5.5 ACCIA with Coarse-Fine Servo-Loop	p. 86
5.5.1 Structure of the ACCIA	p. 86
5.5.2 Coarse Transconductance (CGM) Stage	p. 90
5.5.3 Fine Transconductance (FGM) Stage	p. 94
5.5.4 Integrator Stage	p. 94
5.5.5 Current Balancing IA (CBIA) Architecture	p. 95
5.5.6 Gain Stage	p. 97
5.5.7 Implementation of the ACCIA	p. 97
5.5.8 Fast Start-Up of the ACCIA	p. 99
5.5.9 Power-Noise Performance of the ACCIA	p. 100
5.5.10 Measurement of Performance	p. 102
5.5.11 Comparison with State-of-the-Art	p. 105
5.6 Chopping Spike Filter	p. 106
5.7 Low-Power Programmable Gain Stage	p. 107
5.8 Readout Front-End Channel Test Results	p. 109
5.9 Square Wave Relaxation Oscillator	p. 110
5.10 Analog-to-Digital Converter	p. 113
5.10.1 Basic Operation Principle	p. 113
5.10.2 Architecture	p. 114
5.10.3 Capacitive DAC Implementation	p. 117
5.10.4 Low-Offset Comparator Implementation	p. 119
5.10.5 Test Results	p. 123
5.11 Impedance Measurement and Calibration Modes	p. 125
5.12 Biological Test Results	p. 129
5.13 Summary of the Biopotential Acquisition ASIC	p. 129
5.14 Conclusions	p. 131
6 Wireless Biopotential Acquisition Systems	p. 135
6.1 Introduction	p. 135
6.2 A Wireless VEMP Acquisition System	p. 136
6.3 A Wireless Two-Channel ExG Acquisition System	p. 137
6.4 A1cm3 WirelessEight-ChannelEEGAcquisitionSystem	p. 141
6.5 Conclusions	p. 145
7 Conclusions	p. 147
7.1 Achievements	p. 147
7.2 Suggestions for Future Work	p. 149
Appendix	p. 151
References	p. 157
Index	p. 163

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