Estudo da realimentação em modo comum em um amplificador totalmente diferencial

Abstract

This work describes the design of a fully differential operational transconductance amplifier (OTA) based on the single-output cascode current mirror topology. In addition, the integration of a common-mode feedback (CMFB) circuit initially in near-ideal form and in more practical approaches are discussed, aiming the stabilization of the common-mode voltage of the OTA output terminals. The goal is to present a study of the feedback circuits in order to understand their advantages and disadvantages. Some of these topologies are then designed with the 180 nm Complementary Metal-Oxide-Semiconductor (CMOS) technology and the supply voltage of the circuits is 1.8 V. Finally, the results of the simulations with the different feedback circuits applied to the amplifier are presented, in which the common mode levels at the outputs are successfully preserved and the differential responses have reasonable distortions for the gain obtained.