Fully differential low-noise amplifier with offset reduction for high-resolution neural signal recording

A prototype of a high-density multielectrode array for in vitro recording of electrogenic cell networks has been developed. On a surface of 1.92x1.92mm2, it includes 32x32 pixels with a dimension of 60x60µm2. For local amplification of the sensed extracellular signals, two fully differential lownoise amplifiers with offset reduction circuit have been designed. According to simulations, they feature a programmable gain of 50/60 dB, a bandwidth of 10 kHz and less than 7µVrms of input referred noise at a power consumption of 250µW. The fully differential architecture makes the amplifiers virtually immune against substrate noise. By means of the on-chip logic, each pixel can be selected individually at any time. This allows to monitor the entire cell culture, small portions of it or any preselected set of sites at a high sampling rate. The chip has been designed and fabricated in UMC 180 nm, 3.3V technology. In this paper, simulation results and a first electrical characterisation of the amplifiers are presented.