Systems and method for improving operation of a radio frequency system are provided. One embodiment includes a switching power amplifier that outputs an amplified analog electrical signal based on an input electrical signal and voltage of an envelope voltage supply rail. The switching power amplifier includes a first transistor with a gate that receives the input electrical signal, a source electrically coupled to the envelope voltage supply rail, and a drain electrically coupled to an output of the switching power amplifier; a second transistor with a gate that receives the input electrical signal, a source electrically coupled to ground, and a drain electrically coupled to the output; and a third transistor with a gate that receives the input electrical signal, a drain electrically coupled to the envelope voltage supply rail, and a source electrically coupled to an output of another switching power amplifier.

A method and a device for amplifying an input signal include a power amplifier for amplifying a binary input signal, a modulation device for generating the binary input signal on the basis of the input signal, the input signal being a complex-valued signal and the binary input signal being a real-valued signal, the modulation device including an adding device configured to add the complex-valued input signal to a complex-valued carrier signal of a predefined frequency and to thus generate a resulting complex-valued signal, and the modulation device including a combination device connected downstream from the adding device and configured to generate the real-valued binary input signal from the real part and the imaginary part of the resulting complex-valued signal by combining the real part and the imaginary part of the resulting complex-valued signal.

The disclosure presents a method and an amplifier system for minimizing variation in an acoustical signal caused by variation in gain of an amplifier, comprising a battery for providing a supply voltage to the amplifier, a digital signal processor for providing the acoustical signal to the amplifier, a controller unit receiving an enablement signal when the supply voltage is in an offset mode, and based on the enablement signal requesting a measured voltage during a time period, and a first analog-to-digital converter configured for measuring the supply voltage to the amplifier when receiving the request from the controller unit or the first analog-to-digital converter is configured for measuring the supply voltage to the amplifier continuously, and where variations in the measured voltage relates to variations in the supply voltage during the time period. Furthermore, the controller unit is configured to predict offset modes (i.e. changes) in the supply voltage based on the enablement signals and a fitting of the measured voltages, and wherein the controller unit is configured to generate a compensating signal based on the fitting and transmit the compensating signal to the digital signal processor, the digital signal processor is then configured to minimize variation in the acoustical signal at the output of the amplifier by compensating the variation in gain of the amplifier based on the compensating signal.

Brownout management for an audio amplification system. An audio amplification system includes audio volume control circuitry, audio sample interpolation circuitry, and brownout management circuitry. The brownout management circuitry includes brownout detection circuitry and brownout response circuitry. The brownout detection circuitry is configured to determine whether a voltage of a battery that powers the audio amplification system is below a brownout threshold, and to generate a brownout detection signal that indicates the voltage is below the brownout threshold. The brownout response circuitry is coupled to an audio output of the audio sample interpolation circuitry. The brownout response circuitry is configured to attenuate the audio samples output by the audio sample interpolation circuitry responsive to the brownout detection signal indicating that the voltage is below the brownout threshold.

Brownout management for an audio amplification system. An audio amplification system includes audio volume control circuitry, audio sample interpolation circuitry, and brownout management circuitry. The brownout management circuitry includes brownout detection circuitry and brownout response circuitry. The brownout detection circuitry is configured to determine whether a voltage of a battery that powers the audio amplification system is below a brownout threshold, and to generate a brownout detection signal that indicates the voltage is below the brownout threshold. The brownout response circuitry is coupled to an audio output of the audio sample interpolation circuitry. The brownout response circuitry is configured to attenuate the audio samples output by the audio sample interpolation circuitry responsive to the brownout detection signal indicating that the voltage is below the brownout threshold.

A class-D amplifier includes measurement of speaker current via the low-side drive transistors of the amplifier. In one embodiment, a class-D amplifier includes two high-side transistors, two low-side transistors, a first sense resistor, a second sense resistor, and a sigma delta analog to digital converter (σΔ ADC). The two high-side transistors and two low-side transistors are connected as a bridge to drive a bridge tied speaker. The first sense resistor is connected between a first of the low-side transistors and a low-side reference voltage. The second sense resistor is connected between a second of the low-side transistors and the low-side reference voltage. The ΣΔ ADC is coupled to the bridge to measure voltage across the first sense resistor and the second sense resistor.

A class D amplifier circuit receives an analog audio signal with a first reference voltage as its center level, and outputs an output pulse signal having a duty cycle that corresponds to the analog audio signal. A bias circuit generates a second reference voltage having a voltage level obtained as a division of the first reference voltage and the power supply voltage. A periodic voltage generating circuit of the class D amplifier circuit generates a periodic voltage having a triangle waveform or otherwise a sawtooth waveform having an amplitude that corresponds to the second reference voltage.

A class D amplifier circuit receives an analog audio signal with a first reference voltage as its center level, and outputs an output pulse signal having a duty cycle that corresponds to the analog audio signal. A bias circuit generates a second reference voltage having a voltage level obtained as a division of the first reference voltage and the power supply voltage. A periodic voltage generating circuit of the class D amplifier circuit generates a periodic voltage having a triangle waveform or otherwise a sawtooth waveform having an amplitude that corresponds to the second reference voltage.

Aspects of the present disclosure relate to apparatus and methods for dynamically adjusting the common-mode input signal of a power amplifier, such as a class-D power amplifier. One example power amplifier circuit generally includes a first amplifier having a signal input and a power input; and a common-mode adjustment circuit having a first input coupled to the power input of the first amplifier, having an output coupled to the signal input of the first amplifier, and being configured to generate a common-mode signal to apply to the signal input of the first amplifier, based on a power supply voltage on the power input of the first amplifier.

Aspects of the present disclosure relate to apparatus and methods for dynamically adjusting the common-mode input signal of a power amplifier, such as a class-D power amplifier. One example power amplifier circuit generally includes a first amplifier having a signal input and a power input; and a common-mode adjustment circuit having a first input coupled to the power input of the first amplifier, having an output coupled to the signal input of the first amplifier, and being configured to generate a common-mode signal to apply to the signal input of the first amplifier, based on a power supply voltage on the power input of the first amplifier.