TIPD189, HeadPhone Amplifier for Voltage-Output Audio DACs Reference Design. This reference design details a high-fidelity HeadPhone amplifier circuit suitable for portable applications, such as SmartPhones and tablets. It uses an operational amplifier (Op-Amp) with low power consumption and a very small package to convert a differential output voltage to a single-ended signal suitable for HeadPhones. The design achieves -110.2dB THD+N at >50mW of output power into 32 O HeadPhones