This document describes a filterless high efficiency mono 1.4W class-D audio amplifier with built-in output stage. The amplifier provides 1.4W into 8Ω speaker at 5.0V supply with less than 1% THD and achieves 85% efficiency. It has a signal-to-noise ratio better than 98dB and operates on a single supply from 2.5V to 5.0V. The amplifier features ultralow shutdown current of 20nA and provides short-circuit and thermal protection. It is suitable for applications such as mobile phones, MP3 players, portable gaming devices, and educational toys.