A power module at least includes an ET (Envelope Tracking) module. The ET module includes a buck converter, an inductor, and a capacitor. The buck converter is coupled to a work voltage. The buck converter has a first input terminal for receiving a first control signal, a second input terminal coupled to a supply node, and a buck output terminal The inductor is coupled between the buck output terminal of the buck converter and the supply node. The capacitor is coupled between the supply node and a ground voltage. The ET module is configured to supply a first adaptive supply voltage at the supply node. The first adaptive supply voltage is determined according to the first control signal.