Design of high-order class-D audio amplifiers

This paper presents a design methodology for high-order class-D amplifiers, which covers the entire design flow, from specifications to component sizing. The methodology is validated with three design examples, namely a second-order, a third-order, and a fourth-order class-D amplifier. Moreover, the third-order class-D amplifier has been integrated on silicon and characterized, further confirming the validity of the whole design flow. The achieved results demonstrate that high-order class-D amplifiers can achieve Total-Harmonic-Distortion (THD) performance compatible with the specifications of high-end audio applications (THD ≈ 90 dB), which would be unfeasible with conventional first-order class-D amplifiers.