Low power integrated potentiostat design for μ electrodes with improved accuracy

μelectrodes measuring smaller than 10 μm in size are seen as necessary for improving spatial resolution for detecting bio-activities at the cellular level. Improving measurement accuracy for μelectrodes is important due to their reduced signal magnitudes. Low power design of biosensor circuits with low bias current levels causes large random device mismatches in the potentiostat op amps, which must be calibrated out using offset correction. In addition, μelectrodes are prone to fowling due to their size. Conventional offset cancellation techniques using switched capacitor circuits can reduce the life time of μelectrodes. This paper presents an on-chip potentiostat design with a built-in offset correction circuit that is not detrimental to the life time of μelectrodes. The offset correction technique presented in this paper uses feedback amplifiers that are connected to the body terminals of the relevant PMOS devices in the potentiostat op amp to reduce the offset voltage. The full potentiostat design was implemented in the TSMC 0.18μm process. Simulation results showed an improvement of offset voltage from ±26mV to ±1mV.