A low-noise demultiplexing system for active multichannel microelectrode arrays

The authors report a low-noise demultiplexing system capable of reconstructing multichannel single-unit neural signals derived from multiplexed microelectrode arrays. The overall multiplexing-demultiplexing system realizes ten channels, a per-channel gain of 68 dB, a bandwidth from 100 Hz to 6 kHz, and an equivalent noise level (referred to the probe input) of 13 mu V RMS. It provides for signaling over the power supply to allow the control of on-chip probe functions such as self-testing. The interchannel crosstalk is less than 3%, and switching noise is suppressed by blanking the transition intervals. The 200-kHz probe sample clock is tracked automatically over a range of 150 to 250 kHz. Neural signals as low as 20 mu V (typically 640 mu V at the demultiplexing system input) can be reconstructed. The overall system organization is compatible with the demultiplexing of as many as 40 time-multiplexed electrode channels from a single probe data line.