Design and measurements of 64-channel ASIC for neural signal recording

This paper presents the design and measurements of a low noise multi-channel front-end electronics for recording extra-cellular neuronal signals using microelectrode arrays. The integrated circuit contains 64 readout channels and was fabricated in CMOS 0.18 mum technology. A single readout channel is built of an AC coupling circuit at the input, a low noise preamplifier, a band-pass filter and a second amplifier. In order to reduce the number of output lines, the 64 analog signals from readout channels are multiplexed to a single output by an analog multiplexer. The chip is optimized for low noise and matching performance with the possibility of cut-off frequencies tuning. The low cut-off frequency can be tuned in the 1 Hz - 60 Hz range and the high cut-off frequency can be tuned in the 3.5 kHz -15 kHz range. For the nominal gain setting at 44 dB and power dissipation per single channel of 220 muW the equivalent input noise is in the range from 6 muV - 11 muV rms depending on the band-pass filter settings. The chip has good uniformity concerning the spread of its electrical parameters from channel to channel. The spread of gain calculated as standard deviation to mean value is about 4.4% and the spread of the low cut-off frequency is on the same level. The chip occupies 5times2.3 mm² of silicon area.