The disclosure presents a method and an amplifier system for minimizing variation in an acoustical signal caused by variation in gain of an amplifier, comprising a battery for providing a supply voltage to the amplifier, a digital signal processor for providing the acoustical signal to the amplifier, a controller unit receiving an enablement signal when the supply voltage is in an offset mode, and based on the enablement signal requesting a measured voltage during a time period, and a first analog-to-digital converter configured for measuring the supply voltage to the amplifier when receiving the request from the controller unit or the first analog-to-digital converter is configured for measuring the supply voltage to the amplifier continuously, and where variations in the measured voltage relates to variations in the supply voltage during the time period. Furthermore, the controller unit is configured to predict offset modes (i.e. changes) in the supply voltage based on the enablement signals and a fitting of the measured voltages, and wherein the controller unit is configured to generate a compensating signal based on the fitting and transmit the compensating signal to the digital signal processor, the digital signal processor is then configured to minimize variation in the acoustical signal at the output of the amplifier by compensating the variation in gain of the amplifier based on the compensating signal.

A class D amplifier circuit receives an analog audio signal with a first reference voltage as its center level, and outputs an output pulse signal having a duty cycle that corresponds to the analog audio signal. A bias circuit generates a second reference voltage having a voltage level obtained as a division of the first reference voltage and the power supply voltage. A periodic voltage generating circuit of the class D amplifier circuit generates a periodic voltage having a triangle waveform or otherwise a sawtooth waveform having an amplitude that corresponds to the second reference voltage.

An audio amplifier with duty ratio control is provided. The audio amplifier comprises a pulse width modulation modulator, a power stage, and a voltage converter. The pulse width modulation modulator is configured to receive an input signal for generating a pulse width modulation signal. The power stage is configured to output an output signal according to a supply voltage and the pulse width modulation signal. The voltage converter is configured to adjust voltage level of the supply voltage according to the pulse width modulation signal. The audio amplifier is configured to adjust the voltage level of the supply voltage when duty ratio of the pulse width modulation signal is greater than a duty ratio threshold.

An acoustic apparatus includes a class-D amplifier including a current feedback circuit, and a speaker system including a voice coil driven by the class-D amplifier. The speaker system is configured such that, in a case where the speaker system is driven by an ordinary amplifier having a first output resistance lower than a second output impedance of the class-D amplifier, a Q factor of the speaker system falls below a predetermined lower limit of an ordinary Q factor range of an ordinary speaker system. The current feedback circuit is configured to increase the second output impedance of the class-D amplifier by feeding a current flowing to the voice coil back to an input of the class-D amplifier so as to increase a Q factor as the acoustic apparatus higher than the predetermined lower limit of the ordinary Q factor range and within the ordinary Q factor range.

Provided is a regulator circuit that supplies an output voltage to a load, the regulator circuit including an error amplifier that amplifies an error between a feedback signal and a reference voltage, and an output stage that changes the output voltage, the error amplifier including a first transconductance amplifier that receives the feedback signal and the reference voltage, a first resistance connected to an output node of the first transconductance amplifier and a ground, a first capacitor connected in parallel to the first resistance, a second transconductance amplifier that receives a voltage of the output node of the first transconductance amplifier and the feedback signal, a second resistance connected to an output node of the second transconductance amplifier and a ground, a second capacitor connected in parallel to the second resistance, and a zero controller that controls a gain of the second transconductance amplifier.

One example includes a differential amplifier, a voltage weighting element, coupled to a voltage source which provides an input voltage, to provide a reference voltage with a constant power limit when the input voltage varies, an error amplifier configured to receive and compare the reference voltage provided from the voltage weighting element and a feedback sensed voltage provided from the differential amplifier to identify whether the sensed voltage exceeds the reference voltage, and a pulse width modulation (PWM) controller, coupled to a power transformer and the error amplifier, that reduces a transformer input current provided to the power transformer based on the comparison of the reference voltage from the voltage weighting element and the feedback sensed voltage from the differential amplifier.

Methods, apparatus, and systems are disclosed that adjust transient response in a multistage system. An example apparatus includes a first filter including an input configured to be coupled to an output of a master stage, an amplifier, the first input of the amplifier coupled to the input of the first filter, the second input of the amplifier coupled to the output of the first filter, a second filter, the input of the second filter coupled to the output of the amplifier, and a comparator, the first input of the comparator coupled to the input of the first filter circuit, the second input of the comparator coupled to the output of the amplifier, the third input of the comparator coupled to the output of the second filter, and the output of the comparator adapted to be coupled to a latch.

Disclosed are a digital audio power amplifier and a power amplifier loop. The power amplifier loop comprises an operational amplifier U1, a capacitor C1, a power amplifier output stage, a resistor R1, a resistor R2 and a noise control unit, wherein an inverting input end of the operational amplifier U1 is respectively connected to one end of the capacitor C1, one end of the noise control unit and an output end of a preceding DAC current source; an output end of the operational amplifier U1 is respectively connected to a control end of the power amplifier output stage and the other end of the capacitor C1; an output end of the power amplifier output stage is successively grounded by means of the resistors R1, R2; the other end of the noise control unit is connected to a connection point between the resistors R1, R2; the resistance values of the resistors R1, R2 are set to satisfy R1/R2=(N−2)/2, where N>2; the reference voltage of the operational amplifier U1 is equal to PVDD/N, with PVDD being a power supply voltage of the power amplifier output stage; and the noise control unit is a resistor module. The present application ensures the normal operation of the digital audio power amplifier.

A liquid ejecting apparatus includes a drive circuit that outputs a drive signal, wherein the drive circuit includes a modulation circuit that modulates a base drive signal to output a modulation signal, an amplifier circuit that amplifies the modulation signal to output an amplified modulation signal, a demodulation circuit that demodulates the amplified modulation signal to output the drive signal, and a substrate on which the modulation circuit, the amplifier circuit, and the demodulation circuit are provided, wherein the substrate includes a first face and a second face opposite to the first face, wherein the demodulation circuit includes a first coil and a second coil electrically coupled in parallel with the first coil, and wherein the first coil is positioned so as to overlap at least part of the second coil in a direction normal to the first face.

A signal processer is configured to decrease total harmonic distortion plus noise of an output signal generated from an input signal. The signal processer includes a mixer, a pulse-width modulator, a power stage circuit, and a feedback circuit. The mixer is configured to mix the input signal and a feedback signal to generate a mixed signal. The pulse-width modulator is configured to module the mixed signal to generate a modulated signal and output the modulated signal from an output terminal of the pulse-width modulator. The power stage circuit is configured to amplify the modulated signal to generate the output signal and output the output signal from an output terminal of the power stage circuit. The feedback circuit is configured to generate a feedback signal selectively according to the modulated signal or the output signal.