A feed-forward approach for DC cancellation in fully-differential instrumentation amplifiers

DC suppression consists of a mandatory procedure in several measurement applications. In many situations, its value is orders of magnitude above the desired information to be measured. In fully-differential instrumentation amplifiers, which present a very high common-mode rejection ratio, matched coupling capacitors are demanded for CMRR not to degrade. Stability problems can arise if active cancellation is employed. This paper presents a fully-differential instrumentation amplifier with DC suppression that employs a feed-forward scheme. A mathematical analysis of the proposed circuit is conducted in order to predict its behavior, followed by simulations and experimental measurements for analysis and validation. An excelent performance is achieved, even with standard precision components.