Stability and Compensation Technique for a CMOS Amperometric Potentiostat Circuit for Redox Sensors

The stability and compensation of a closed loop CMOS amperometric potentiostat circuit used in many electrochemical sensors is investigated in this paper. The redox sensing technique utilizes a mass-transport limited current through micro-electrodes submerged in an analyte assay which can be modeled as a current source in parallel with a fractal parasitic R-C impedance. Using a current amplifier topology, detailed circuit analysis and simulation indicates that the phase margin may degrade into instability due to the microelectrode parasitic impedance which contributes a relatively non-dominant pole. A suitable technique for the compensation of the potentiostat circuit is also discussed