VLSI potentiostat for amperometric measurements for electrolytic reactions

This paper describes a CMOS integrated potentiostatic control circuit. The design maintains a constant bias potential between the reference and working electrodes for an amperometric chemical sensor. A technique of converting input currents into time for amperometric measurements is proposed. Redox currents ranging from a 1 pA to 200 nA can be measured with a maximum nonlinearity of ± 0.1% over this range. Analog inputs are processed and digital outputs are generated without requiring a power-hungry A/D converter. A prototype chip has been fabricated in the 0.5 μm AMI CMOS process. Experimental results are reported showing the performance of the circuit as a chemical sensor.