Active Electrodes for Wearable EEG Acquisition: Review and Electronics Design Methodology

Abstract

Abstract-Active Electrodes (AE), i.e. electrodes with built-in readout circuitry, are increasingly being implemented in wearable healthcare and lifestyle applications due to AE's robustness to environmental interference. An AE locally amplifies and buffers µV-level EEG signals before driving any cabling. The low output impedance of an AE mitigates cable motion artifacts thus enabling the use of high-impedance dry electrodes for greater user comfort. However, developing a wearable EEG system, with medical grade signal quality on noise, electrode offset tolerance, common-mode rejection ratio (CMRR), input impedance and power dissipation, remains a challenging task. This paper reviews state-of-the-art bio-amplifier architectures and low-power analog circuits design techniques intended for wearable EEG acquisition, with a special focus on AE system interfaced with dry electrodes. Index Terms-Active electrode, instrumentation amplifier (IA), electroencephalography (EEG), dry electrodes, common-mode rejection ratio (CMRR), brain-computer interface (BCI)I. INTRODUCTION ecent advances in biomedical technologies, integrated circuits (ICs), sensors and data analysis techniques have accelerated the development of wearable technology for Telehealth applications. Today, miniature and low-power medical sensors can be easily integrated into various accessories that continuously sense, process and transfer people's physiological information during their daily life activities. By reducing the need for manual intervention and by lowering the cost, these medical devices are being widely used in personal healthcare and home diagnostics, such as wellness and health monitoring, home rehabilitation, and the early detection of brain disordersElectroencephalography (EEG)

11nW Signal Acquisition Platform for Remote Biosensing

“…Due to its unprecedentedly low energy dissipation for a biosensing platform, the system's power consumption is orders of magnitude lower than any reported work. The summary of requirements for wearable EEG systems using active electrodes in [13] provides a set of specifications that should be met to perform reliable readouts with a wireless solution and it will be used as a reference for this paper. Similarly, [14] shows the performance requirements for neuro-recording amplifiers in implantable devices, which -in terms of power-are still orders of magnitude higher than the proposed solution.…”

“…OF WEARABLE EEG APPLICATIONS[13], NEURO-RECORDING AMPLIFIERS[14],AND THE PERFORMANCE OF THIS WORK Neuro-recording amplifiers per conversion and transmission, with 12.3µV rms input referred noise over a 1.48 kHz band. While operating at a sampling and communication rate of 256 Hz, the power consumption is 10.94 nW.…”

Low Noise, High Input Impedance Digital-Analog Hybrid Offset Suppression Amplifier for Wearable Dry Electrode ECG Monitoring

“…However, the flaw is its high electrode-skin impedance. Typical dry-electrode impedance is in a range from a few hundreds of kiloohms to a few tens of megaohms [3], leading to a large signal attenuation and a significant increase in noise and offset [4].…”

A Review of Issues Related to Data Acquisition and Analysis in EEG/MEG Studies

“…The study of social interactions between individuals has prompted the coupling of multiple EEG/MEG systems to one another; the method is often called hyperscanning [14]. Developments in technology are now also allowing portable dry-electrode EEG [15,16,17,18] to be used in naturalistic environments. In all of these cases, it is critical to preserve the integrity and quality of the data despite the considerable increase in experimental complexity.…”