Abstract A micropower amperometric potentiostat, suitable for use in cost-sensitive analytical sensors has been built and characterised in our laboratory. The low-power, low-cost and miniature design makes this potentiostat potentially attractive for use in handheld, portable and battery powered electrochemical instruments and sensors where component cost, size, or power consumption, may be at a premium. The potentiostat uses a novel analogue to digital converter (ADC) circuit that allows the direct conversion of electrode currents in the nanoampere range to low-voltage CMOS logic levels using four operational amplifiers. The digital output of the potentiostat is suitable for direct interfacing to microprocessors, removing the need for expensive external, or on-chip, ADC’s. Specific characteristics of the embodiment we have evaluated are a current consumption of 260 μA, operation down to 2.5 V dc, a total component volume of less than 3 cm 3 , and a component cost of approximately 5 Euros for prototype quantities.