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.