Described are a circuit for compensating non-linearities essentially without changing a characteristic curve operating point and/or operating range, having: an alternating voltage signal source for providing an input signal; a control unit which receives the input signal and converts it to a predistorted signal depending on at least one preset predistortion parameter; and a sink for receiving the predistorted signal, the sink being coupled to an adjusting unit configured to provide the sink with an adjusting signal, to operate the sink in an operating range or at an operating point, the control unit being configured to receive at least one sensor signal of the sink in a feedback manner and to adapt the at least one preset predistortion parameter based on the at least one sensor signal, and a corresponding method.

Resistor mismatch may be digitally compensated based on a known resistor mismatch, power supply information, and/or other operating parameters of the amplifier. The digital compensation may be applied to the digital input signal before conversion for processing and amplification in the analog domain. An amplifier with digital compensation for resistor mismatch may be used in a class-D amplifier with a closed loop and feedforward feedback. A class-D or other amplifier with digital compensation may be integrated with electronic devices such as mobile phones.

A method may include, in an apparatus comprising a closed loop amplifier and a signal processing block configured to generate an amplifier input signal as a function of an upstream signal received at an input of the signal processing block, in a calibration mode of the apparatus: decoupling a second stage input of the amplifier from a first stage output of the amplifier; determining an offset signal that when applied to the input of a signal processing block as the upstream signal generates approximately zero as an intermediate signal generated by the first stage of the amplifier; and controlling one or more parameters of the apparatus based on the offset signal to compensate for an offset of at least one of the first stage and the signal processing block.

An audio processing system reduces perception of audible artifacts due to changes in an element in an audio channel of the audio processing system. The system reproduces an audio input signal and produces an audio output signal with the audio channel. The channel has an adjustable or selectable element that, responsive to a control signal, changes a characteristic of the audio processing channel, which generates a transient in the audio output signal. The systems include a level detector for measuring a signal level of the audio input signal and a controller responsive to an output of the level detector to determine a masking time interval available from the audio output signal due to signal content in the audio input signal. The controller generates the control signal to change the characteristic of the audio processing channel so that at least a portion of the transient occurs in the masking time interval.

Resistor mismatch may be digitally compensated based on a known resistor mismatch, power supply information, and/or other operating parameters of the amplifier. The digital compensation may be applied to the digital input signal before conversion for processing and amplification in the analog domain. An amplifier with digital compensation for resistor mismatch may be used in a class-D amplifier with a closed loop and feedforward feedback. A class-D or other amplifier with digital compensation may be integrated with electronic devices such as mobile phones.

A digital amplifier includes a digital PWM generator, a first amplifier circuit, a first low-pass filter, a second amplifier circuit, a second low-pass filter, an attenuator, an error extractor, an adder, and a voltage supply unit. The first amplifier circuit amplifies a digital PWM signal at a second voltage. The first low-pass filter extracts a low-frequency band voltage signal from the amplified digital PWM signal, and outputs the extracted voltage signal to a load. The second amplifier circuit amplifies the generated digital PWM signal at a third voltage. The error extractor extracts an error signal. The adder adds a digital error signal whose feedback gain is adjusted to a digital audio signal. The voltage supply unit generates the third voltage that has a voltage value of a predetermined ratio to a voltage value of the second voltage, and supplies the third voltage to the second amplifier circuit.

This application relates to audio amplifier circuitry (100). An amplifier module (103) is located in a signal path between an input (101) and an output (102). A detection module (106) is configured to detect a characteristic of a load (104) electrically coupled, in use, to the output. A distortion setting controller (107) is provided for selecting one of a plurality of stored distortion settings {p.sub.i} based on the detected characteristic of the load; and a pre-distortion module (105) is configured to apply a first transfer function to a signal in the signal path prior to said amplifier module. The first transfer function is based on the selected distortion setting and for at least one of the stored distortion settings the corresponding first transfer function comprises a non-linear distortion function.

This application relates to audio driving circuits having good audio performance. The circuit (301) has a forward signal path between an input (103) for receiving an input audio signal (S.sub.IN) and an output (104) for outputting an output signal (S.sub.OUT) with an amplifier module (102) in the forward signal path. An error block (302) is arranged to receive a first signal (S.sub.FF) derived from the input signal and also a second signal (S.sub.FB) derived from the output signal and determine a first error signal (.sub.1) indicative of a difference between the first and second signals. A first processing module (204) is operable to generate a compensation signal (S.sub.C) to be applied to the input signal (S.sub.IN) upstream of the amplifier module (102) based on the first error signal. The error block (302) comprises a second processing module (303/303a) configured to apply a linear transfer function to one of the first signal or the second signals prior to determining the first error signal. In some embodiments the second processing module may apply a linear transfer function which is adaptive based on a second error signal (.sub.2) indicative of the error between the first and second signals after the linear transfer function has been applied.

This application relates to methods and apparatus for amplification of audio signals with improved audio performance. An audio driving circuit (200) has an amplifier module (102) in a forward signal path between an input (103) for receiving an input audio signal (S.sub.IN) and an output for outputting an audio driving signal (V.sub.OUT). A pre-distortion module (202) is operable to apply a first transfer function to the signal in the forward signal path upstream of the amplifier module, wherein the first transfer function comprises a non-linear distortion function based on at least one distortion setting. An error block (203) is arranged to receive a first signal (S.sub.FF) derived from the input signal and a second signal (S.sub.FB) indicative of the voltage of the audio driving signal and determine a first error signal (.sub.1) indicative of a difference between the first and second signals. The pre-distortion module (202) is operable to control the distortion setting(s) based on the first error signal.

A piece of audio equipment is provided that includes a first signal path including a first dynamic range expander and a lowpass filter. The piece of audio equipment also includes a second signal path parallel to the first signal path, wherein the second signal path includes a second dynamic range expander and a highpass filter. The piece of audio equipment further includes a summing amplifier configured to receive a first signal from the first signal path, a second signal from the second signal path, and a clear signal from an audio source and output a summed signal.