A Performance-Aware Low-Quiescent Headphone Amplifier in 65-nm CMOS

A low-quiescent high-performance class-AB headphone amplifier is presented. The effect of the input-referred offset on the quiescent power of audio power amplifier (APA) that drives very small resistive load is described and analyzed. A digitally assisted offset calibration-based APA topology together with improved frequency compensation is proposed. This permits the use of low quiescent power and small compensation capacitance. Implemented in 65-nm CMOS technology, the amplifier occupies an area of 0.15 mm(2) and consumes 0.4 mW at +/- 1 V supplies. At the load of 16 Omega//200 pF, the gain-bandwidth product is 1.78 MHz using a total compensation capacitance of 8.5 pF. Other performance metrics are measured with -89-dB total harmonic distortion (THD+ N), 93.5-dB signal-to-noise ratio, 84-dB power supply rejection ratio (PSRR+), and 105-dB PSRR-@ 217 Hz. It can deliver a peak power of 35 mW (1.5 Vpp swing) to the above load, yielding the best figure-of-merit (FOM) = (peak load power/quiescent power) and the best FOM2 = [peak load power/quiescent power * (THD+ N)%] with respect to other reported representative works.