Artefact-suppressing analog spike detection circuit for firing-rate measurements in closed-loop retinal neurostimulators

The aim of this research is to investigate low-power circuit concepts for the hardware implementation of adaptive stimulation for future retinal implants. Especially for retinal implants, the circuit complexity must be low while increasing functionality. This paper presents the implementation of an analog spike detection circuit to perform electrode individual firing-rate measurements in a spatially high-density electrode array, which has a reduced circuit complexity compared to the wide-used nonlinear energy operator (NEO) and allows stronger suppression of local oscillations due to the retinal remodeling. This recording-unit is integrated in an eight-channel closed-loop-neurostimulator prototype. This recording unit dissipates 13.8 µW and requires an area of 0.066 mm 2 by using a 350 nm CMOS process.