24-Channel EEG Readout Front-End ASIC

The existing multi-channel EEG acquisition systems make use of off-the-shelf components for the implementation of the analog readout front-end. This not only consumes an excessive amount of power but also increases the size of the system that limits the autonomy of the patient. Therefore, there is a need for a multi-channel ASIC that is tailored towards the low-power and the small size needs of the biopotential acquisition systems.

This Chapter describes a 24-channel EEG readout front-end ASIC that can circumvent the above mentioned problems of size and power for the EEG acquisition systems with large number of channels. It is capable of extracting biopotential signals from conventional Ag/AgCl biopotential electrodes. Sect. 3.2 describes the architecture of the 24-channel EEG readout front-end ASIC. Each channel of the ASIC uses a CBIA architecture that is described in Sect. 3.3 to filter the out of band signals and to reject the common-mode interference. Furthermore, Sect. 3.4 introduces a new CMRR reduction mechanism called electrode offset induced common-mode gain and demonstrates that this reduction mechanism is dominant for the IAs that are being used under large differential DC offset voltage between the biopotential electrodes. Later, Sect. 3.5 describes the gain stage of the channels that is for the further amplification of the output of the CBIA. Sect. 3.6 presents the test results of the ASIC, and Sect. 3.7 states the conclusions of this Chapter.