A low voltage rail-to-rail operational amplifier with constant operation and improved process robustness

Abstract

An operational amplifier is one of the most basic components in analog, mixedsignal, RF, and other integrated circuit designs. Low voltage and low power operational amplifier design has become an increasingly interesting subject as many applications switch to portable battery powered operations. The need for design techniques to allow amplifiers to maintain an acceptable level of performance when the supply voltages are decreased is immense. One of the most important features in low voltage amplifier designs is ensuring that the amplifier maintains constant behavior in the presence of rail-to-rail input commonmode variations while providing a rail-to-rail output to maximize signal-to-noise ratio. In this work a new rail-to-rail low voltage operational amplifier is designed, simulated, and compared against state of the art amplifier designs. The amplifier architecture aims at achieving constant amplifier operation over a rail-to-rail common-mode input voltage range. The concept of constant operation refers to the ability to maintain constant specifications such as gain, gain-bandwidth product, phase margin, slew rate, and power consumption against large variations in input common-mode voltage. The amplifier is additionally designed to be robust with respect to variations in process parameters, supply voltages, and operating temperatures (PVT). A final evaluation of the performance of the proposed design versus that of the state of the art in the open literature is carried out. The intended capabilities and advantages of the new design are verified through extensive simulation.