A class D amplifier output stage including an input for receiving an input signal, an output for providing an output signal to a load, serially coupled upper and lower switching devices configured to provide an output signal to the output, a driver circuit configured to receive the input signal, and to derive therefrom first and second drive signals for driving the upper and lower switching devices alternately from a conducting state into a non-conducting state and vice versa, such that the conducting state periods of the upper switching device with respect to those of the lower switching device are mutually exclusive and separated by dead time intervals during which both upper and lower output transistors are non-conducting. To reduce distortion and more particularly, total harmonic distortion (THD), the amplifier output stage includes a substantially linear circuit configured to provide a bidirectional current sink for residual currents from the load occurring during at least part of each dead time interval.

The present disclosure relates to an integrated circuit comprising a transconductance amplifier which is connectable to a microelectromechanical systems (MEMS) transducer. The transconductance amplifier comprises a first input coupled to a first current conveyor and a second input coupled to a second current conveyor for converting a single-ended or differential transducer signal voltage into an intermediate signal current representative of the transducer signal voltage through a shared reference resistor. The transconductance amplifier further comprises first and second output circuits coupled to the shared reference resistor and being configured to convert the intermediate current signal into a corresponding differential output current signal through first and second output terminals for driving a load.

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.

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 sense amplifier circuit comprising a first-, second-, third- and fourth-amplification-blocks, each amplification-block comprising: an amplification-block-transistor comprising and an amplification-block-resistor. The amplification-block-transistor includes: a first-conduction-channel-terminal, a second-conduction-channel-terminal that is connected to an amplification-block-output-node, and a control-terminal that is connected to an amplification-block-control-node. The sense amplifier circuit also comprises: an amplification-block-resistor connected in series between an amplification-block-input-node and the first-conduction-channel-terminal; a first-bias-voltage-source connected to the amplification-block-control-nodes of the first- and third-amplification-blocks, a second-bias-voltage-source connected to the amplification-block-control-nodes of the second- and fourth-amplification-blocks. The sense amplifier circuit also comprises: a first-common-mode-voltage-resistor connected in series between a first-sensed-output-terminal and a common-mode-voltage-node; and a second-common-mode-voltage-resistor connected in series between a second-sensed-output-terminal and the common-mode-voltage-node.

A sense amplifier circuit comprising a first-, second-, third- and fourth-amplification-blocks, each amplification-block comprising: an amplification-block-transistor comprising and an amplification-block-resistor. The amplification-block-transistor includes: a first-conduction-channel-terminal, a second-conduction-channel-terminal that is connected to an amplification-block-output-node, and a control-terminal that is connected to an amplification-block-control-node. The sense amplifier circuit also comprises: an amplification-block-resistor connected in series between an amplification-block-input-node and the first-conduction-channel-terminal; a first-bias-voltage-source connected to the amplification-block-control-nodes of the first- and third-amplification-blocks, a second-bias-voltage-source connected to the amplification-block-control-nodes of the second- and fourth-amplification-blocks. The sense amplifier circuit also comprises: a first-common-mode-voltage-resistor connected in series between a first-sensed-output-terminal and a common-mode-voltage-node; and a second-common-mode-voltage-resistor connected in series between a second-sensed-output-terminal and the common-mode-voltage-node.

A Bridge-Tied Load output self-oscillating class D amplifier includes a comparator receives an input signal from a signal input circuit at a second input terminal and outputs a positive-phase pulse width modulation signal and a reverse-phase pulse width modulation signal by comparing voltages of the two input terminal, first and second switching circuits power-amplifies the reverse-phase pulse width modulation signal and the positive-phase pulse width modulation signal, a first low-pass filter extracts a first output signal from the reverse-phase pulse width modulation signal, a second low-pass filter extracts a second output signal from the positive-phase pulse width modulation signal, a subtractor calculates a difference between the first and second output signals and output a difference signal, and a first feedback circuit feeds back the difference signal to the second input terminal of the comparator.

A Bridge-Tied Load output self-oscillating class D amplifier includes a comparator receives an input signal from a signal input circuit at a second input terminal and outputs a positive-phase pulse width modulation signal and a reverse-phase pulse width modulation signal by comparing voltages of the two input terminal, first and second switching circuits power-amplifies the reverse-phase pulse width modulation signal and the positive-phase pulse width modulation signal, a first low-pass filter extracts a first output signal from the reverse-phase pulse width modulation signal, a second low-pass filter extracts a second output signal from the positive-phase pulse width modulation signal, a subtractor calculates a difference between the first and second output signals and output a difference signal, and a first feedback circuit feeds back the difference signal to the second input terminal of the comparator.

Certain aspects of the present disclosure provide an amplifier for signal amplification. Certain aspects further describe methods and apparatus for applying overload protection for such amplifier. For example, one method generally includes detecting an overload condition of an amplifier based on a signal at a node of the amplifier, and controlling a parameter of an input signal of the amplifier such that the parameter of the input signal is maintained below a threshold based on the detection of the overload condition. The parameter of the input signal may include, for example, a voltage level or a duty cycle of the input signal.

Certain aspects of the present disclosure provide an amplifier for signal amplification. Certain aspects further describe methods and apparatus for applying overload protection for such amplifier. For example, one method generally includes detecting an overload condition of an amplifier based on a signal at a node of the amplifier, and controlling a parameter of an input signal of the amplifier such that the parameter of the input signal is maintained below a threshold based on the detection of the overload condition. The parameter of the input signal may include, for example, a voltage level or a duty cycle of the input signal.