Search

In this paper we present a measurement system for in vivo multichannel recordings of the electrophysiological activity of brain tissue. The system consists of penetrating Microelectrode Array (MEA), three versions of a Conditioning Module each equipped with different Application Specific Integrated Circuits (ASIC), Digitizer and PC Application for recorded data presentation and storage. The MEA consists of 64 15 μm diameter microelectrodes. The multichannel ASICs amplify and filter field and action potential signals. The custom-made Digitizer Module simultaneously acquires data from all channels with a 14 kS/s sample rate and 12 bit resolution. The resulting byte stream (about 2 MB/s) is transmitted to the PC via USB (Universal Serial Bus). Eventually the measurement data is decoded, presented to the system user and stored on a HDD. Preliminary system tests confirm its excellent performance (low input refereed noise, low power consumption, low area occupancy, ability of Action Potentials/Local Field Potentials separation). Our system equipped with multichannel ASICs meets requirements of many different neurobiology experiments.

This paper presents design and measurement results of an integrated circuit dedicated to recording and detecting a wide range of biomedical signals. The chip is designed in 180 nm CMOS technology and occupies 1.5×1.5 mm 2 . It consists of 8 channels responsible for amplification, filtration and detection of biomedical signals. In order to satisfy the requirements of a wide range of neurobiological experiments, the main parameters of a single recording channel, such as voltage gain, frequency band, voltage offset and threshold detection, are controlled independently by on-chip digital registers. The recording part is divided into two separate channels, i.e. an Action Potential (AP) stage and a Local Field Potential (LFP) stage. The voltage gain of the AP and LFP stages can be switched between 55.7/50.3 dB and 50.3/45.1 dB respectively. Corner frequencies of a particular stage can be digitally controlled in a wide range, i.e. the upper cut-off frequency can be changed in the 20 Hz–2 kHz (LFP stage) while the lower cut-off frequency can be tuned at the 120 mHz–3 kHz (LFP and AP stage). The upper cut-off frequency of the AP stage is equal to 6.9 kHz. In addition, the area of the analog part of the recording channel is 0.04 mm 2 . A single recording channel is supplied from ±0.9 V and consumes about 4.8 µW of power while the Input Referred Noise is equal to 6.2 µV resulting in 4.92 of Noise Efficiency Factor (NEF).