Integrated Class-D Amplifier With Active Current Sensing Suitable for Alternating Current Switches

An integrated class-D amplifier with active current sensing suitable for ac switches is presented in this paper. The proposed current-sensing technique is used to sense and control the inductor current at the output stage and allows the current-sensing element to be integrated into class-D amplifiers. To verify the performance of the proposed circuits, a class-D amplifier was designed and fabricated with 3.3-V 0.35- $\mu\hbox{m}$ double-polyquadruple-metal CMOS technology on a chip area of 1.79 $\times$ 1.45 mm. The maximum power efficiency of the class-D amplifier can be up to 94% for an 8-$\Omega$ load. These active current-sensing circuits can be applied to other power converters with ac switches.