Design of a CMOS Potentiostat Circuit for Electrochemical Detector Arrays

摘要

High-throughput electrode arrays are required for advancing devices for testing the effect of drugs on cellular function. In this paper, we present design criteria for a potentiostat circuit that is capable of measuring transient amperometric oxidation currents at the surface of an electrode with submillisecond time resolution and picoampere current resolution. The potentiostat is a regulated cascode stage in which a high-gain amplifier maintains the electrode voltage through a negative feedback loop. The potentiostat uses a new shared amplifier structure in which all of the amplifiers in a given row of detectors share a common half circuit permitting us to use fewer transistors per detector. We also present measurements from a test chip that was fabricated in a 0.5-$mu$m, 5-V CMOS process through MOSIS. Each detector occupied a layout area of 35 $mu$m$,times,$ 15 $mu$m and contained eight transistors and a 50-fF integrating capacitor. The rms current noise at 2-kHz bandwidth is ${approx}110$ fA. The maximum charge storage capacity at 2 kHz is $1.26 times 10^6$ electrons.