Austriamicrosystems has introduced the AS3560 and AS3561 stereo headphone amplifiers for mobile phones, portable navigation devices, music/media players and other devices that use headphones. Compared with the traditional class AB amplifier, the new 30mW headphone amplifier continuously adjusts the headphone power rail voltage according to the input signal, thus greatly reducing power consumption. This article refers to the address: http:// The AS3560 is a Class G amplifier, and the AS3561 uses a Class H topology to be more energy efficient. Class G topologies can switch between three power rails, while Class H topologies adapt to different headphone volume outputs by adjusting the power rail output. Both devices use differential inputs to minimize the effects of ground noise and EMI sensitivity. The quiescent current when the two channels are open is only 1 mA, and the shutdown current is reduced to less than 5 μA. The AS3560 and AS3561 maintain excellent audio performance with a signal-to-noise ratio greater than 100 dB at 1 Vrms and a 0.02% THD at 16 Ω output, making them a power and audio performance device. The integrated charge pump produces a negative supply that is symmetrical to the input supply, allowing the audio signal to flow back directly to ground, eliminating the need for bulky and expensive DC blocking capacitors, saving space and minimizing system cost. The volume of the left and right channels can be adjusted separately through the I2C interface, and each level is adjustable. Oliver Jones, Austrian marketing manager for microelectronics audio products, said: "Class G products can improve the sound quality of linear headphone drivers and significantly reduce power consumption. This topology is undoubtedly the most effective choice for headphone drive in terms of cost and performance. Class H products go a step further and can use up the battery." The AS3560 and AS3561 are available in a 16-ball 1.6x1.6 mm WL-CSP package. The AS3560 is priced at $0.95 per 1,000 pieces and the AS3561 is priced at $0.98 per thousand. Both products operate from -30 to +85 °C.