For high-throughput electrophysiology with planar patch-clamp electrodes there is a need for extremely dense amplifier arrays.We have fabricated two complete computer-controlled, whole-cell amplifiers on a single 3 × 3 mm silicon-on-sapphire die.The amplifiers have fast-capacitance, series-resistance and leak compensation, along with integrated analog filters for the stimulus input and current-monitor output.The power consumption is about 3 mW per amplifier.These amplifiers will form part of a complete high-density recording system.