A 120nm CMOS Fully Differential Rail-to-Rail I/O Opamp with Highly Constant Signal Behavior

This paper proposes a fully differential opamp implemented in 120 nm digital CMOS technology, with rail-to-rail input common-mode range, realized by a novel approach of constant small- and large-signal behavior control. The small-signal response is improved to an extremely slim deviation of 2.4%. Also a new class-AB rail-to-rail output stage is designed, targeting at high drive capability down to 33Omega resistive load, high power transfer efficiency and linearity. A modified measurement circuitry for fully differential opamps is introduced as well.