Stability Analysis and Novel Compensation of a CMOS Current-Feedback Potentiostat Circuit for Electrochemical Sensors

This paper discusses the stability and novel compensation of a closed-loop CMOS amperometric potentiostat circuit used in many redox electrochemical sensors. The redox sensing technique utilizes a mass-transport limited current through microelectrodes 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 analysis and simulation indicates that the phase margin may degrade into instability due to the microelectrode parasitic impedance which contributes a relatively nondominant pole. A novel technique for the compensation of the potentiostat circuit is also presented, and, its robustness is also verified through extensive Monte Carlo simulations