A 50µm pitch, 1120-channel, 20kHz frame rate microelectrode array for slice recording

We present a 1,120 channel active microelectrode array with 50μm pitch recording sites for direct recording of neural slices. Every sensor site has a frontend low noise amplifier and photopixel for correlating optical stimulus with electrical activity. The frontend is AC-coupled and achieves area-efficiency by integrating the large input capacitor and recording electrode directly over the circuitry in conjunction with a single T-capacitor feedback network. Degraded PSRR (63dB) and CMRR (21dB) from the single feedback network are overcome by utilizing a virtual shared reference, improving rejection to 84dB and 66dB, respectively. Despite a small area, the frontend amplifier has an input-referred noise of 4.3μVrms with tunable high- and low-pass corners with very little variation from site-to-site. Experiments from a transgenic mouse olfactory bulb slice are shown. The array was implemented in a standard 180nm CMOS process.