An 82-mW ΔΣ-Based Filter-Less Class-D Headphone Amplifier With −93-dB THD+N, 113-dB SNR, and 93% Efficiency

A low-power 113-dB SNR, −93-dB total harmonic distortion (THD)+N, digital input
$\Delta \Sigma $
-based filter-less Class-D amplifier for wireless headphone applications is presented. This performance is achieved by the following architecture improvements: 1) variable-frequency-
$\Delta \Sigma $
Class-D with digital feed-forward and switching-frequency reduction, 2) common-mode-stabilized power stage, 3) current digital-to-analog converter direct drive, and 4) rotational first-order dynamic-element-matching techniques. It operates on a single 1.8-V power supply with no external passive components except for a supply decoupling capacitor. The Class-D headphone amplifier achieves 82-mW non-clipping output power with 93% efficiency at a 16-
$\Omega $
and 33-
$\mu \text{H}$
load condition. The complete system was fabricated in a 40-nm CMOS process and occupies 1.33-mm
²
die area.