A 0.028% THD+N, 91% power-efficiency, 3-level PWM Class-D amplifier with a true differential front-end

A Class-D amplifier (CDA) is best suitable for audio mobile applications due to its high-power efficiency, thus enabling to remove a bulky heat sink. A traditional Class-D amplifier uses a 2-level output switching scheme. There typically exist an external LC filter and a bulky capacitor to block a DC average current and to protect the speaker from the current, which increases the bill of materials. As a remedy, a 3-level switching scheme allows to eliminate the filters, hence helping to reduce the system cost. Moreover, the 3-level switching scheme provides additional benefits of less electromagnetic interference and better power efficiency. The 3-level approach prevails with the help of various modulation techniques such as a pulse-width modulation (PWM) [1,2], a sliding-mode control [3], and a uniform PWM [4] method.