Fecha de publicación: 24/01/2019 Fuente: Wipo "digitalization" A digital amplifier includes a digital PWM generator, a first amplifier circuit, a first low-pass filter, a second amplifier circuit, a second low-pass filter, an attenuator, an error extractor, an adder, and a voltage supply unit. The first amplifier circuit amplifies a digital PWM signal at a second voltage. The first low-pass filter extracts a low-frequency band voltage signal from the amplified digital PWM signal, and outputs the extracted voltage signal to a load. The second amplifier circuit amplifies the generated digital PWM signal at a third voltage. The error extractor extracts an error signal. The adder adds a digital error signal whose feedback gain is adjusted to a digital audio signal. The voltage supply unit generates the third voltage that has a voltage value of a predetermined ratio to a voltage value of the second voltage, and supplies the third voltage to the second amplifier circuit.