An implantable CMOS circuit interface for multiplexed microelectrode recording arrays

A second-generation multichannel probe designed for measuring single-unit activity in neural structures is described. The probe includes CMOS circuitry for electronically positioning the recording sites with respect to the active neurons and for amplifying and multiplexing the recorded signals. The probe selects eight active recording sites from among 32 on the probe shank using a static input channel selector. The neural signals on the selected channels are then amplified and multiplexed to the outside world. The probe offers a typical AC gain of 300 (15 Hz to 7 kHz), a DC gain of 0.3, and an equivalent input noise of 15 μV rms. Operating from a single 5-V supply, the probe dissipates 2.5 mW of power and implements channel selection, self-testing, data output, and initialization using three external leads. The probe is realized using 12 masks in a high-yield single-sided dissolved wafer process with a 3-μm feature size for the circuitry and a 3-μm pitch on the electrode shanks