A 28-W, -102.2-dB THD+N Class-D Amplifier Using a Hybrid Δ Σ M-PWM Scheme

This article presents a 28-W class-D amplifier for automotive applications. The combination of a high switching frequency and a hybrid multibit $\Delta \Sigma \text{M}$ -PWM scheme results in high linearity over a wide range of output power, as well as low AM-band EMI. As a result, only a small (150-kHz cutoff frequency), and thus low-cost, LC filter is needed to meet the CISPR-25 EMI average limit (150 kHz–30 MHz) with 10-dB margin. At 28-W output power, the proposed amplifier achieves 91% efficiency while driving a 4- $\Omega $ load from a 14.4-V supply. It attains a peak THD+N of 0.00077% (−102.2 dB) for a 1-kHz input signal.