A device includes a variable gain amplifier, a voltage shifter, a variable gain amplifier half replica module, and an analog to digital converter. The variable gain amplifier includes an input terminal to receive an input signal, an output terminal to provide a first output signal that is biased based on a first common-mode voltage reference. The voltage shifter circuit includes first and second input terminals, and an output terminal to provide, to the analog to digital converter, a third output signal that is biased based on a second common-mode voltage reference. The variable gain amplifier half replica module includes an output terminal coupled to the second input terminal of the voltage shifter circuit, the variable gain amplifier half replica module to control the third output signal of the voltage shifter circuit based on the first common-mode voltage reference and the second common-mode voltage reference.

A filterless high-efficiency class D power amplifier (HEPA) exploits the phase relationships of even and odd harmonics at transistor drains of a push-pull topology to eliminate output filtering, enabling an ultra-high-efficiency, low harmonic signal. The filterless HEPA relieves the amplifier of a requirement for a power consuming filter by implementing a high-quality operational harmonic block on an output stage without output buffering. The operational harmonic block senses the voltage source radio frequency to the amplifier prior to waveform squaring and employs a harmonic canceling balun to block even harmonics (in-phase) but pass odd harmonics (180° out of phase). The sensed ideal voltage source shunts the odd-harmonic currents to ground, leaving only the fundamental current on its primary to pass to the load.

A protection circuit for an acoustic filter and/or a power amplifier is disclosed. In one aspect, the protection circuit includes a bidirectional coupler that helps secure a measurement of power at an antenna. The power measurement is compared to a threshold by a detector, and if the power measurement is above the threshold, a signal is sent that causes debiasing of a power amplifier stage, which reduces power levels of signals being amplified by the power amplifier stage and correspondingly lowers the power level going through a filter associated with the power amplifier stage. By lowering the power level going through the power amplifier stage and the filter, both elements are protected against over power conditions allowing functionality to be maintained.

A circuit for driving a capacitive load includes an amplifier for driving the load based on an input signal, the amplifier comprising at least a boost converter, a dynamic model configured to track a capacitance of the load and a voltage of the source for powering at least parts of the circuit, an adaptive filter, configured to filter the input signal based on an output of the dynamic model.

An amplifier includes a differential input stage, a hysteresis stage, coupled to the differential input stage, a cascode stage coupled to the hysteresis stage, a feedback stage coupled to an output of the cascode stage and configured to provide a feedback signal to the hysteresis stage, and an output stage coupled to the output of the cascode stage. The output stage includes a hysteresis inverter coupled between the output of the cascode stage and the amplifier output.

An amplifier includes a differential input stage, a hysteresis stage, coupled to the differential input stage, a cascode stage coupled to the hysteresis stage, a feedback stage coupled to an output of the cascode stage and configured to provide a feedback signal to the hysteresis stage, and an output stage coupled to the output of the cascode stage. The output stage includes a hysteresis inverter coupled between the output of the cascode stage and the amplifier output.

A device includes a variable gain amplifier, a voltage shifter, a variable gain amplifier half replica module, and an analog to digital converter. The variable gain amplifier includes an input terminal to receive an input signal, an output terminal to provide a first output signal that is biased based on a first common-mode voltage reference. The voltage shifter circuit includes first and second input terminals, and an output terminal to provide, to the analog to digital converter, a third output signal that is biased based on a second common-mode voltage reference. The variable gain amplifier half replica module includes an output terminal coupled to the second input terminal of the voltage shifter circuit, the variable gain amplifier half replica module to control the third output signal of the voltage shifter circuit based on the first common-mode voltage reference and the second common-mode voltage reference.

Aspects of the disclosure provide an amplifier system and a method for dynamically cancelling an offset voltage. The amplifier system includes a chopper amplifier system that includes a differential amplifier with an offset calibration circuit. The chopper amplifier system is configured to generate an output signal including voltage variations indicating an offset voltage of the differential amplifier. The amplifier system also includes a feedback circuit configured to determine a polarity of the offset voltage of the differential amplifier based on the output signal, and to transmit a control signal to the offset calibration circuit to reduce the offset voltage of the differential amplifier.

A protection circuit for an acoustic filter and/or a power amplifier is disclosed. In one aspect, the protection circuit includes a bidirectional coupler that helps secure a measurement of power at an antenna. The power measurement is compared to a threshold by a detector, and if the power measurement is above the threshold, a signal is sent that causes debiasing of a power amplifier stage, which reduces power levels of signals being amplified by the power amplifier stage and correspondingly lowers the power level going through a filter associated with the power amplifier stage. By lowering the power level going through the power amplifier stage and the filter, both elements are protected against over power conditions allowing functionality to be maintained.