Amplificador de instrumentação em modo corrente com entrada e saída rail-to-rail

Abstract

This dissertation is aimed at the development of a current mode instrumentation amplifier (CMIA) with a high common mode input range. This characteristic is obtained due to the rail-to-rail operational amplifiers (opamps). These opamps are built with rail-to-rail differential amplifiers as input stages, and with cascode-based output stages, which are able to copy its current by adding identical branches and connecting their gates without the voltage degradation as the known CMIA topologies. The main contribution of this work is the development of a rail-to-rail current mode instrumentation amplifier, analyzing the pros and cons of this topology. The functionality of the proposed topology is shown through measured results of a manufactured integrated circuit. This first prototype, although it was operated in a large input common mode range, presented insufficient values of CMRR (Common Mode Rejection Ratio) and VOS (Offset voltage). These two characteristics were studied and modeled, the instrumentation amplifier was re-designed, and simulated results demonstrate important improvements.