Abstract: A class-D amplifier that amplifies an input signal comprises a control circuit configured to generate a control signal that varies in accordance with a level of the input signal, a first generating circuit configured to generate a first pulse, and a second generating circuit configured to generate a second pulse. A pulse width of the first pulse becomes narrower as the signal level of the input signal becomes smaller, and the pulse width of the first pulse becomes wider as an instantaneous magnitude of the input signal becomes larger. A pulse width of the second pulse becomes narrower as the signal level of the input signal becomes smaller, and the pulse width of the second pulse becomes wider as an instantaneous magnitude of the input signal becomes smaller.

Abstract: A class-D amplifier includes: a gain control unit that amplifies an input audio signal in accordance with a compensation gain to generate an input signal Vin; and a pulse width modulator that generates a first pulse Vp whose pulse width changes according to the input signal Vin within a first input range A1 where a value of the generated input signal Vin is higher than a first boundary Vb1, and that generates a second pulse Vn whose pulse width changes according to the generated input signal Vin within a second input range A2. The gain control unit controls the compensation gain so that first inclination of an input/output characteristic of the class-D amplifier in a first section in which the pulse width modulator outputs both the first pulse Vp and the second pulse Vn and second inclination of the input/output characteristic in a second section other than the first section are similar to each other.

Abstract: Pulse width modulators 131P and 131N respectively generate a first pulse Vp whose pulse width changes according to an input signal Vin based on the input signal Vin and a generated first carrier wave C1P, and a second pulse Vn whose pulse width changes according to the input signal Vin based on the input signal Vin and a generated second carrier wave C1N. Wherein due to the non-liner gradient in each of the generated first carrier wave C1P and the generated second carrier wave C1N and, duty ratio of each of the generated first pulse Vp and the generated second pulse Vn is less than 50% in a state where a value of the input signal is zero; and a difference between a pulse width of the first pulse Vp and a pulse width of the second pulse Vn linearly changes according to the input signal Vin.

Abstract: An audio device includes a base portion a power supply circuit arranged on the base portion and configured to output electric power; a rotation body rotatably supported by the base portion and configured to, upon rotation of the rotation body, move a playback point of a piece of music; an electric circuit arranged on the rotation body; and a non-contact power feeding mechanism configured to supply in a non-contact manner the electric power output by the power supply circuit to the electric circuit in which the non-contact power feeding mechanism is arranged on a path from the power supply circuit to the electric circuit.

Abstract: An audio device includes a base portion a power supply circuit arranged on the base portion and configured to output electric power; a rotation body rotatably supported by the base portion and configured to, upon rotation of the rotation body, move a playback point of a piece of music; an electric circuit arranged on the rotation body; and a non-contact power feeding mechanism configured to supply in a non-contact manner the electric power output by the power supply circuit to the electric circuit in which the non-contact power feeding mechanism is arranged on a path from the power supply circuit to the electric circuit.