Class G audio power amplifier uses two (or more) separate voltage supplies with different levels, take the benefit of AB class amplifier when operated its  almost full signal swing.  With two different level of supply voltage, the efficiency is significantly improved while maintaining the best accuracy (low distortion) of linear amplifier. The LM48824 is a Class G, ground-referenced stereo headphone amplifier, designed for portable devices. The LM48834 has National’s ground-referenced architecture which eliminate the large DC blocking capacitors which is required by traditional headphone amplifiers, keeping the cost low and saving the space.

Class G Power Amplifier with LM48824 circuit schematic

The LM48824 takes advantage of National’s patent-pending Class G architecture which is offering power savings compared to a traditional Class AB headphone amplifier. Additionally, by common-mode sensing that corrects for any differences between the amplifier ground and the potential at the headphone return terminal, the output noise is improve. This will minimize noise created by any ground mismatches.

The LM48824′s outputs is allowed to be driven by an external source without degrading the signal by high output impedance mode. Other features include flexible power supply requirements, low power (2.5uA) shutdown mode, differential inputs for improved noise rejection, and a 32-step I 2C volume control with mute function.

Audible transients on power-up/down and during shutdown is eliminated by the LM48824′s superior click and pop suppression. The LM48824 is available in an ultra-small 16-bump, 0.4mm pitch micro SMD package (1.69mm x 1.69mm). [Circuit’s schematic diagram source: National Semiconductor Application Note]