Active-pixel / multiplexed electrode array

An electrode array in which each site, or small cluster of sites, has its own active circuitry — typically an in-pixel amplifier and a switch — so that a large number of sites can share a small number of output wires by time-division or frequency-division multiplexing. This is distinct from a passive array, where every electrode needs its own dedicated wire and the wire count becomes the hard scaling limit.

Active multiplexing is the circuit principle behind high-density CMOS probes and large-area surface (electrocorticography) grids alike. Its costs are real: multiplexing trades wire count for bandwidth and power per line, adds switching noise and settling constraints, and concentrates failure risk — a shared readout line or a clock fault can take down many channels at once.