ADA489x Rail-to-Rail Output Amplifiers Analog Devices Inc. ADA489x Rail-to-Rail Output Amplifiers are unity-gain stable, 1nV/√Hz high-speed, low-noise voltage feedback amplifiers with a quiescent current of 3mA. Developed using Analog Devices’ proprietary next-generation SiGe bipolar process and innovative architecture, the ADA489x Amplifiers provide high-performance operation.