This invention enables to efficiently improve the signal-to-noise power ratio of a delta-sigma modulator without increasing the operating frequency. A digital modulation device 40 includes: a setting unit 41 that sets mutually different default values for N delta-sigma modulation units 42-1 to 42-N; N delta-sigma modulation units 42-1 to 42-N that input signals for each clock cycle indicated in a first clock signal and then perform delta-sigma modulation on the input signals to output modulated signals including noise signals having values that change in accordance with default values; and a serial output unit 43 that inputs, in order, the modulated signals output by the delta-sigma modulation units 42-1 to 42-N for each clock cycle indicated in a second clock signal, the second clock signal having a clock cycle that is 1/N of the clock cycle of the first clock signal, and then serializes and outputs the modulated signals.

Provided is a digital acoustic system comprising: a ΔΣ modulator that modulates a digital input signal and outputs a digital signal; a post-filter that is connected to the ΔΣ modulator and which performs mismatch shaping to convert the digital signal; a parallel-serial converter that converts the digital signal converted by the post-filter into a digital signal which is serially transmitted; a serial-parallel converter that restores the digital signal converted by the parallel-serial converter; and a drive circuit which receives the digital signal restored by the serial-parallel converter, and drives drive elements to convert the signal into an analog audio signal.

Embodiments of the disclosure are drawn to apparatuses a hybrid switched capacitor array power amplifier (H-SCPA). The H-SCPA may have an array of storage elements divided into sub-arrays. A first sub-array may be configured to receive a delta sigma modulated (DSM) signal. A second sub-array may be configured to receive a Nyquist-rate signal. The H-SCPA may provide an output based on the received DSM and Nyquist-rate signals. The first sub-array and second sub-array may have different architectures. The DSM signal may represent the least significant bits of the signal and the Nyquist-rate signal may represent the most significant bits of the signal.

An audio amplifier system is described comprising: a variable gain audio processor for processing digital audio signal, a digital to analog converter coupled to the audio processor, and configured to receive the processed digital audio signal, a variable gain amplifier having an input coupled to the output of the digital to analog converter and operably connected to a power supply, a controller coupled to the variable gain audio processor and the variable gain amplifier and configured to switch the audio amplifier system between a first operating mode having a first power supply voltage value and a second operating mode having a second higher power supply voltage value; wherein the controller is operable in the first operating mode to set the audio amplifier system gain to a desired gain value and in the second operating mode to maintain the desired gain value.

Certain aspects of the present disclosure provide amplifiers. Certain aspects of the present disclosure provide methods and apparatus for protecting an such amplifiers, for example an audio amplifier, or a delta-sigma modulator from saturation. One example amplifier generally includes an output stage comprising a plurality of transistors; and a feedback network having an input coupled to an output of the output stage and comprising a plurality of integrators connected in series. At least one of the plurality of integrators generally includes an operational amplifier having an input and an output, a first resistive element coupled to the input of the operational amplifier, a capacitive element coupled between the input and the output of the operational amplifier; and a first switch coupled between the input and the output of the operational amplifier. For certain aspects, the amplifier may be a class-D amplifier or a direct digital feedback amplifier (DDFA).

A transmitter according to the present invention includes: a baseband amplitude value distribution processor (90) for changing a distribution of an amplitude value of a baseband signal based on a control signal that has been input and outputting the baseband signal as an output signal; a digital transmitter (91) that ΔΣ modulates the output signal and transmits the modulated signal; an in-band distortion measurement unit (92) for measuring an in-band distortion amount of the output signal; an amplitude value distribution measurement unit (93) for calculating an amplitude value distribution of the output signal; a sideband distortion prediction unit (94) for predicting a sideband distortion amount occurring in the output signal by the digital transmitter (91) from the calculated amplitude value distribution; and a baseband processing controller (95) for adjusting the control signal based on the measured in-band distortion amount and the sideband distortion amount and outputting the adjusted signal.

A Class-D amplifier includes a plurality of power rails, a quantizer, and a driver stage. The quantizer and the driver stage have a combined gain. For each power rail of the plurality of power rails, the Class-D amplifier senses a voltage value for the power rail and determines a ramp amplitude based on the sensed voltage value. The Class-D amplifier concurrently switches from the driver stage using a first power rail to a second power rail of the plurality of power rails and switches from the quantizer using the ramp amplitude associated with the first power rail to using the ramp amplitude associated with the second power rail so that the combined gain is constant.

A transmitter, a transmission system and a transmission method whereby AM-PM distortions can be compensated with high accuracy without affecting the functions of a predistortor, a ΔΣ modulator and so on. The transmitter includes: a baseband signal generation circuit that outputs the amplitude value and phase value of a baseband signal; a ΔΣ modulation circuit that performs a ΔΣ modulation of the outputted amplitude and phase values to output a pulse signal train; a power supply modulation circuit that supplies, to a pre-stage amplifier, a voltage determined in accordance with the outputted amplitude value; the pre-stage amplifier and a post-stage amplifier that amplify the outputted pulse signal train; and a filter circuit that generates an output signal from the pulse signal train as amplified and outputs the output signal. The power supply modulation circuit determines the voltage for canceling a phase error occurring in the post-stage amplifier.

A system includes an audio amplifier, a duty cycle detector, a channel equalizer, and a sample-and-hold circuit. The audio amplifier is configured to amplify an analog audio signal to produce an amplified audio signal. The duty cycle detector is configured to generate a saturation detect signal at a first state upon detection that the amplified audio signal produced by the audio amplifier is clipped. The channel equalizer is configured to generate an initial estimate of a speaker terminal voltage. The sample-and-hold circuit is configured to sample and hold the initial estimate of the speaker terminal voltage as a final estimate of the speaker voltage when the saturation detect signal is in the first state.

An integrated circuit can include an amplifier coupled to receive an analog input signal, an anti-aliasing filter (AAF) coupled to an output of the amplifier, a buffer circuit coupled to an output of the AAF, a sigma-delta modulator configured to generate a digital data stream in response to an output of the buffer, and a plurality of chopping circuits nested within one another, including a first pair of chopping circuits having at least the amplifier disposed therebetween and configured to remove offset in the analog input signal, and a second pair of chopping circuit having at least the first pair of chopping circuits disposed therebetween. The amplifier, AAF, sigma-delta modulator, and chopping circuits can be formed with the same integrated circuit substrate. Corresponding methods and systems are also disclosed.