Yamaha Corporation

Masato Miyazaki

Tatsuya Kishii

Masayoshi Nakamura

Toshio Maejima

Hirotoshi Tsuchiya

Akihisa Himeno

Hirotaka Kawai

Ken Makino

Moritaka Iyoda

An offset cancel circuit includes a first amplifying section, a second amplifying section, a third resistor connected between a non-inverting input terminal of the first amplifying section and a non-inverting input terminal of the second amplifying section, and a current source. In the offset cancel circuit, the current source causes a constant current to flow through the third resistor to cancel an offset voltage from output signals of first and second amplifying sections, the constant current corresponding to the offset voltage contained in first and second output signals output from a bridge resistance type sensor.

Offset cancel circuit

A charge pump includes a switching circuit which is interposed among first and second output capacitors, a flying capacitor, and an input power supply; and a control unit which controls the switching circuit. The charge pump is operated in an operation mode including a high-voltage outputting mode, a low-voltage outputting mode, and a relay mode. The control unit controls the switching circuit so that respective charging voltages of the first and second capacitors that are charged in the high-voltage outputting mode are gradually lowered. The control unit changes the operation mode of the charge pump by relay transition from the high-voltage outputting mode through the relay mode to the low-voltage outputting mode when a voltage lower command is given during a period when the operation mode of the charge pump is in the high-voltage outputting mode.

Charge pump

A class-D amplifier for generating from an input signal a digital signal for driving a load, includes an output limit instruction generating section that detects that the digital signal falls outside a limit range and that outputs an output limit instruction signal, an attenuation instruction pulse generating section that includes an integrator for integrating the output limit instruction signal and that outputs a periodical attenuation instruction pulse having pulse width corresponding to an integrated value in the integrator, an attenuating section provided in an input path for the input signal and that attenuates the input signal based on the attenuation instruction pulse, and a mute control section that controls the integrated value in the integrator independently of the output limit instruction signal to control an amount of the attenuation of the attenuating section applied to the input signal.

Class-D amplifier

An amplifying device includes a selecting section that selects one of a first power source potential and a second power source potential which are different from each other, a potential generating circuit that generates a third power source potential from the power source potential selected by the selecting section, an amplifier that operates with supply of the first power source potential and the third power source potential, and a controlling circuit that variably controls a target to be selected by the selecting section in accordance with at least one of an amplitude of a signal on an input side of the amplifier, an amplitude of a signal on an output side of the amplifier, and the third power source potential.

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Hamamatsu, Japan

Masato Miyazaki