A 200 μW Eight-Channel EEG Acquisition ASIC for Ambulatory EEG Systems

• Published in: IEEE journal of solid-state circuits Vol. 43; no. 12; pp. 3025 - 3038
• Main Authors: Yazicioglu, Refet Firat, Merken, Patrick, Puers, Robert, Van Hoof, Chris
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.12.2008; Institute of Electrical and Electronics Engineers
• Subjects: AC coupling; analog integrated circuits; Analog-digital conversion; Application specific integrated circuits; Applied sciences; bio potential amplifier; Biomedical imaging; Calibration; chopper modulation; Choppers; Circuit properties; Design. Technologies. Operation analysis. Testing; Electric, optical and optoelectronic circuits; electrocardiography; electrode offset; Electrodes; Electroencephalography; electromyography; Electronic circuits; Electronics; Exact sciences and technology; Hardware; Input-output equipment; instrumentation amplifier; Instruments; Integrated circuits; Low-noise amplifiers; Power dissipation; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Signal convertors; Performance evaluation; Noise figure; Implementation; electrode offset; electrocardiography; AD converter; Energy dissipation; User interface; Complementary MOS technology; High performance; electroencephalography; Calibration; chopper modulation; Readout electronics; Power consumption; analog integrated circuits; electromyography; Integrated circuit; AC coupling; Biopotential amplifier; Miniaturization; instrumentation amplifier; Low-power electronics; Impedance; Custom circuit; Chopper; Gain; Analogue integrated circuits
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2008.2006462

The growing interest toward the improvement of patients' quality of life and the use of medical signals in nonmedical applications such as entertainment, sports, and brain-computerinterfaces, requires the implementation of miniaturized and wireless biopotential acquisition systems with ultralow power dissipation. Therefore, this paper presents the implementation of a complete EEG acquisition ASIC tailored towards the needs of such applications, i.e., high-signal quality, low-power dissipation and ease of use. The presented ASIC includes eight readout front-end channels and an 11-bit analog-to-digital converter (ADC). The key to its high performance and low-power dissipation is the new AC coupled chopper stabilized instrumentation amplifier (ACCIA) implementation that uses a coarse-fine servoloop and reaches more than 120 dB CMRR, consumes only 2.3 \mu{\hbox{A}} , and achieves a noise-efficiency factor (NEF) of 4.3. Furthermore, the ease of use of the ASIC is realized by incorporating Calibration and Electrode Impedance Measurement Modes to the ASIC. Therefore, the former can be used to check the functionality of the ASIC, as well as, to calibrate the gain matching of the channels, where as the latter can be used to track the quality of the biopotential electrode. The ASIC is implemented in 0.5 \mu{\hbox{m}} CMOS process and the total current consumption is 66 \mu{\hbox{A}} from 3 V.