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Studying brain activity in vivo requires collecting bioelectrical signals from several microelectrodes simultaneously in order to capture neuron interactions. In this work, we present a new current-reuse analog front-end (AFE), which is scalable to very large numbers of recording channels, thanks to its small implementation silicon area and its low-power consumption. This current-reuse AFE, which is including a low-noise amplifier (LNA) and a programmable gain amplifier (PGA), employs a new fully differential current-mirror topology using fewer transistors, and improving several design parameters, such as power consumption and noise, over previous current-reuse amplifier circuit implementations. We show that the proposed current-reuse amplifier can provide a theoretical noise efficiency factor (NEF) as low as 1.01, which is the lowest reported theoretical NEF provided by an LNA topology. A foue-channel current-reuse AFE implemented in a CMOS 0.18-μm technology is presented as a proof-of-concept. T-network capacitive circuits are used to decrease the size of input capacitors and to increase the gain accuracy in the AFE. The measured performance of the whole AFE is presented. The total power consumption per channel, including the LNA and the PGA stage, is 9 μW (4.5 μW for LNA and 4.5 μW for PGA), for an input referred noise of 3.2 μV, achieving a measured NEF of 1.94. The entire AFE presents three selectable gains of 35.04, 43.1, and 49.5 dB, and occupies a die area of 0.072 mm per channel. The implemented circuit has a measured inter-channel rejection ratio of 54 dB. In vivo recording results obtained with the proposed AFE are reported. It successfully allows collecting low-amplitude extracellular action potential signals from a tungsten wire microelectrode implanted in the hippocampus of a laboratory mouse.

This study presents the design of efficient wireless power distribution systems based on resonant inductive arrays. The authors show how to use multi‐resonator arrays to charge and power up several electric devices in parallel, with nearly constant transmitted power, and using a single power source. Their single‐source wireless power transmission clusters, for instance, are shown to provide free positioning at better power efficiency than previous solutions. They provide analysis, simulation, and measurement performance of their multi‐resonator arrays, they compare them with other types of inductive arrays employed into different schemes (multi‐coil inductive links, overlapping and non‐overlapping links), and they show the advantage of their strategy over previous solutions. The presented wireless power distribution systems improve power transmission efficiency (PTE) in free positioning by as much as 30%. The measured results show that their multi‐resonator arrays present significant advantages: (i) they allow multiple charging zones from a single power source; (ii) they provide free positioning with strictly uniform power delivered to the load; and (iii) they provide superior efficiency through a built‐in power localization mechanism, which is not available in other solutions. The PTE of the multi‐resonator array in single‐receiver and multi‐receiver configurations outperformed previous solutions by 26% and 12%, respectively.

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