An approach to fully differential circuit design without common-mode feedback

Abstract

Fully differential transconductance structures allow for greater linearity than their single-ended counterparts. The disadvantage is the need for common-mode feedback circuitry, which complicates the design and introduces additional design problems and constraints. In this paper we present and analyze a new technique for designing fully differential transconductance structures which removes the need for common-mode feedback by instead forming two independent nonlinear transconductance blocks, each of whose common-mode output voltage is well defined by the differential feedback.