A power tube driver of a class-D audio amplifier includes high-side and low-side fixed charge/discharge gate driving circuits, high-side and low-side power tubes, a dead time generation circuit based on gate voltage detection, high-side and low-side gate charge/discharge accelerating circuits, and high-side and low-side gate voltage detection circuits. The class-D audio amplifier with the features of low radiation interference, and high efficiency, linearity and robustness can be balanced easily.