Offset correction of low power, high precision op amp using digital assist for biomedical applications

Op amps created in new process technologies with smaller geometries face the problem of an increasing offset voltage due to a greater sensitivity to process variations and geometry mismatches at smaller channel dimensions. This can negatively impact measurement accuracy when these op amps are used in biomedical measurement systems such as a potentiostat. The conventional technique of increasing transistor gate dimensions to reduce offset has become more difficult to implement due to the limitations on channel length and the growing negative impact on performance in the latest technology nodes. This paper presents a new technique to correct offset voltage of an array of potentiostat op amps that dynamically adjusts the body voltages of a matching pair of PFET´s in the op amp to null out the offset voltage.