Tuning the low cut-off frequency in multichannel neural recording amplifiers by the on-chip correction DACs

This paper presents a design and measurements of multichannel integrated circuits dedicated to recording of neurobiological signals. 64 recording channels have been implemented in a single chip using a commercially available CMOS 180 nm process. A single recording amplifier consumes only 25 μW from 1.8 V supply and occupies 0.13 mm² of the silicon area. Its main parameters such as the low/high cut off frequencies and the voltage gain are controlled thanks to the on-chip register. User is able to change the low cut off frequency in the 60 mHz - 100 Hz range in each channel independently while the high cut off frequency and the voltage gain can be set to 4.7 kHz / 12 kHz and 139 V/V / 1100 V/V respectively. The input referred noise depends on the bandwidth of the recording channel and is equal to 3.7 μV (100 Hz - 12 kHz) or to 7.6 μV (3 Hz - 12 kHz). This paper deals with problems that are present in a multichannel integrated recording electronics for neurobiology experiments such as: ability to record input signals in the frequency range below a single Hz, and the spread of the cut off frequencies from channel to channel in such systems. Up to our knowledge the solution presented in this paper is the first one reporting the multichannel IC that is able both to record extremely low frequency signals in each channel with a small spread of this parameter from channel to channel.