Area reduction techniques for deep-brain probes with electronic depth control

Implanted devices in the brain are required for in-vivo experiments with freely moving animals and will become a key element of future neuronal interfaces, e.g. for prosthetic limbs with neural control. To maintain an optimal signal quality and cope with micro motions of the implant or plastic reorganization of the brain, the concept of electronic depth control was developed. It combines the high spatial resolution of neuron-sized electrodes with the processing power of CMOS electronics. Challenges of such CMOS probes with active assistance arise from the fact that each recording site has to be equipped with a gain stage consuming very little area. This work gives an overview of the most recent high-density neuronal probes and presents solutions for area-efficient implementations of analog signal-processing features, like on-line bandwidth variation or autonomous start-up and common-mode referencing.