An integrated MEG acquisition system with CMOS instrumentation amplifier and offset cancellation

We propose a CMOS-based Magnetoencephalography(MEG) acquisition system. The MEG acquisition system consists of a small-sized high inductance coil sensor and an instrumentation amplifier (IA). The small-sized high inductance coil sensor is fabricated in 0.18 μm standard CMOS process. Output signal sensitivity of MEG acquisition sensor chip is 3.25fT/μV and noise figure of 34.9fT/(√Hz). The IA is designed along with low-pass and high-pass filters to reduce noise. It draws only 540 μA from a standard 3.3V battery, making it suitable for use in portable systems. By using current feedback techniques it achieves a common mode rejection ratio of 120 dB while the total noise referred to input is kept below 0.87 μV.