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.

A wireless communication device configured to prevent a transmission time period for sending a wireless signal and a receiving time period for receiving a wireless signal from being overlap, comprises: a transmitter that includes an orthogonal modulator that orthogonally modulates an IQ-modulated modulation signal and a transmission power amplifier that power-amplifies the orthogonally modulated signal; a receiver that includes a demodulator that demodulates a received signal; a first power source that is the power source for the transmission power amplifier and the receiver; and a second power source that is the power source for the orthogonal modulator; and a controller which outputs the modulation signal to the orthogonal modulator. The first power source outputs a constant voltage to the receiver during the receiving time period, and outputs, during the transmission time period, to the transmission power amplifier, a fluctuating voltage according to an envelope of the modulation 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.

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.

Sampler circuitry, having: an input node which receives an input voltage signal; a primary current path connected between high and low voltage supply nodes; a secondary current path connected between high and low voltage supply nodes; current mirror circuitry; and load circuitry having sampler switches which sample a current signal, where the input node is defined along the primary current path, the primary current path configured to carry a primary current dependent on the input voltage signal; the current mirror circuitry includes a primary side and a secondary side, the primary side connected along the primary current path and the secondary side connected along the secondary current path so that a secondary current dependent on the primary current is caused to flow along the secondary current path; and the load circuitry is connected along the secondary current path so that the secondary current at least partly forms the current signal.

A modulated signal generating device for modulating includes a first amplifier that generates a first amplified signal based on a first control signal; a second amplifier that has a smaller amplification factor as compared to the first amplifier and that generates a second amplified signal based on a second control signal; a combiner that combines the first amplified signal and the second amplified signal and generates a modulated signal; a first control unit that generates the first control signal based on a first component signal included in a input signal; a first filter that eliminates the harmonic component included in a first difference signal, which represents the difference between the input signal and the first component signal, and generates a first filtered signal; and a second control unit that generates the second control signal based on a second component signal included in the first filtered signal.

A multi-path subsystem may include a first processing path, a second processing path, a mixed signal return path, and a calibration engine configured to: estimate and cancel a direct current (DC) offset of the mixed signal return path, estimate and cancel a DC offset between the first processing path and the second processing path, estimate and cancel a phase difference between the first processing path and a sum of the second processing path and the mixed signal return path, estimate and cancel a return path gain of the mixed signal return path, and track and correct for a gain difference between the first processing path and the second processing path.

A supply voltage conditioning circuit comprises a differential amplifier, a comparator, a sample and hold (S/H) circuit, and a delay circuit. The differential amplifier receives an input supply voltage and a reference voltage, and outputs a difference signal. The comparator receives the difference signal and a value representative of a noise margin, and outputs a control signal indicative of whether the difference signal is greater than the value representative of the noise margin. The S/H circuit samples the input supply voltage in response to the control signal indicating the difference signal is greater than the noise margin, and outputs a substantially noise free supply voltage. This allows the output supply voltage to track underlying changes in the input supply voltage but filter out noise in the input supply voltage. The delay circuit receives and delays the output supply voltage to generate the reference voltage.

A dual-mode average power tracking (APT) controller operates in a first mode to move the control voltage quickly without concern for ripple or ringing. When this coarse adjustment takes the control voltage to within a desired margin of a target, the controller may switch to a second mode, where the APT controller more slowly approaches the target, but has reduced ringing or ripples. The mode is changed by changing resistance and capacitance values in a loop filter within the APT circuit. In a further aspect, a pulse shaper circuit may inject a pulse to force the control voltage to change more rapidly. By switching modes in this fashion, the control voltage may quickly reach a desired target, and then remain in the second mode during a transmission time slot such that the control voltage is clean throughout.

A method, applied in a driving circuit including a bidirectional circuit coupled between a voltage source and a load, includes receiving a feedback signal from the load and an input signal; generating a plurality of pulse width modulation (PWM) signals according to the input signal and the feedback signal; driving the load by the bidirectional circuit according to the plurality of PWM signals such that the input signal and the feedback signal are substantially proportional to each other. The input signal is a time varying signal. The step of generating a PWM signal among the plurality of PWM signals according to the input signal and the feedback signal includes determining a difference according to the input signal and the feedback signal; and generating the PWM signal with a pulse width. The pulse width is determined according to the difference.