A cascode-free single-stage amplifier using a fully-differential folded voltage-combiner

This paper presents the design and the electrical simulations of a single-stage amplifier with high energy-efficiency and enhanced DC gain without the need of using any cascode devices or any positive-feedback or feed-forward techniques. Instead, a fully-differential folded voltage-combiner block is used in replacement of the traditional tail current-source that is normally employed to bias the differential-pair. Simulation results of the properly optimized circuit, using AIDA-C, a state-of-the-art multi-objective multi-constraint circuit-level optimization tool, demonstrate that a DC gain above 50 dB can be achieved, together with high energy efficiency. A simulated figure-of-merit above 2200 MHz×pF/mA has been reached. The circuit was designed using a 130 nm CMOS technology, draining approximately 0.2 mA from a 1.2 V power supply.