Extracellular recording system based on amplitude modulation for CMOS microelectrode arrays

Abstract

An innovative readout channel, based on analog amplitude modulation of the signals recorded by each sensing site, is developed for high-density CMOS-based microelectrode arrays. A single amplification stage simultaneously records the neural activity acquired from several sensors. A theoretical analysis has demonstrated that a major physical limitation of the readout architecture relates to the summation of the thermal noise of each recorded signal at the input node of the front-end amplification stage. After implementation of the proposed readout architecture in a UMC 0.18 μm CMOS technology, it has been shown that the maximum number of sensors which can simultaneously be recorded depends on the electrical characteristics of the recorded extracellular voltages, which depend on the experimental setup. Considering a typical case encountered during electrophysiological experiments, the maximum number of sensors which can simultaneously be recorded is approximately in the range of 5-10.

Recent Advances in Neural Recording Microsystems

“…The implementation of such a scheme results in a similar system-level architecture as shown in Figure 1(a) , but with the analog multiplexer relocated before the sensory channels building blocks. A frequency-division multiplexing scheme is implemented in [ 81 ] where the amplitudes of the neural activity seen at each individual electrode is modulated and directed towards a single wideband neural amplifier. It is shown in [ 81 ] that the maximum number of electrodes that can be multiplexed towards one single amplifier is limited by the summation of the thermal noise from each site at the input node of the wideband neural amplifier, which is in the range of 5 to 10 for typical cases.…”