Three is a Crowd for Instrumentation Amplifiers

Abstract: Three-op-amp instrumentation amplifiers have long been the industry standard for precision applications that require high gains and/or high CMRR. However, these amplifiers have serious limitations when operating from the single-supply voltage rails required in many modern applications. This article explains the limitations of the conventional three-op-amp architecture for instrumentation amplifiers, and introduces Maxim's indirect current-feedback architecture that offers specific advantages for single-supply operation of instrumentation amplifiers. Detailed analysis is supported by laboratory waveforms.