Noise performance design of preamplifiers for silicon microelectrodes with on-chip electronics

A systematic design guideline for the noise performance of preamplifier of the active semiconductor neural probe is presented. Analysis of signal-to-device-noise ratio (SNR) for CMOS source follower buffer and two-stage differential voltage amplifier is given, based on a measured extracellular recording from Aplysia, and 1/f noise spectrum measurement. Important factors having significant effects on the SNR are determined, Analytical expressions of the output noise power are derived and utilized to tailor the parameters controllable by the circuit designer. We show that the output device noise power can be much higher than the output signal power if the devices at the input stage of the preamplifier were made as small as given CMOS fabrication technology permits. Quantitative information of the preamplifier circuit parameters for satisfactory noise performance is provided.