Projeto automático de amplificadores operacionais totalmente diferenciais em tecnologia CMOS

Abstract

Fully differential amplifiers play a critical role in systems which differential signaling is present. One drawback of this kind of amplifier is the need of an extra circuit, called Common-Mode Feedback (CMFB), to keep its output voltages stable. This work presents a automatic design methodology of fully differential operational amplifiers in CMOS technology, where the main and CMFB circuits are consider. The methodology is implemented within the design flow of an optimization-based automatic synthesis tool. The methodology consists in two parts. At first moment, an ideal CMFB model is used in order to reduce the number of free variables to the optimization heuristic. This strategy improves the convergence of the optimization process once the design space is reduced. Following, the real CMFB circuit is designed. The methodology is validated through the design of a one-stage fully differential amplifier in CMOS 0.18 𝜇m technology. In order to verify the suitability of the methodology for more complex design, as well its generality, the design of a two-stage fully differential amplifier using a no capacitor feed-forward (NCFF) compensation technique in 0.13 𝜇m CMOS technology is presented. The obtained simulation results showed satisfactory to the imposed constraints. Therefore, showing the suitability of the methodology to the design of high performance fully differential operational amplifiers.