A 160μW 8-channel active electrode system for EEG monitoring

An important drawback of current biopotential monitoring systems is their dependence on gel electrodes, which can dry out, cause skin irritation, and necessitate skilled personnel. These associated drawbacks increase the running costs and significantly hamper their use in consumer healthcare and lifestyle applications. Unfortunately, the use of gel-free, or dry, electrodes increases the electrode-tissue contact impedance, thus exacerbating the effects of interference and cable motion artifacts. A solution is the use of active electrodes, i.e. electrodes in which an amplifier with high input impedance, low noise and good electrode offset rejection is co-integrated (Fig. 17.1.1). Previous active electrodes employed voltage buffers to facilitate the inter-channel gain matching necessary to achieve high CMRR [1]. However, low-noise buffers consume significant power and due to their lack of gain still require a low-noise and thus power-hungry back-end to keep the total integrated noise at acceptable levels. To reduce the total power dissipation, this paper proposes a biopotential monitoring system based on active electrodes with gain.