A power amplifier (PA) circuit includes a circuit for generating a supply voltage at an upper voltage rail for a power amplifier (PA). The circuit includes a DC-to-DC converter for generating a voltage from which the supply voltage is generated; a linear amplifier for sourcing or sinking current to or from the upper voltage rail via a capacitor for performing fine adjustment of the supply voltage; a first switching device coupled between an output of the linear amplifier and a lower voltage rail to selectively assist the linear amplifier sink current through the capacitor to deal with actual or anticipated transient response of the supply voltage; and a second switching device coupled between the upper voltage rail and the lower voltage rail to selectively discharge the capacitor in response to actual or anticipated transient response of the supply voltage.

Apparatus and methods for power amplifier distortion networks are disclosed. In one aspect, there is provided a power amplifier system including a power amplifier configured to amplify a radio frequency input signal. The power amplifier including an input configured to receive the radio frequency input signal and an output configured to generate an amplified radio frequency signal. The power amplifier system further includes a distortion network electrically coupled to either the input or the output of the power amplifier. The distortion network including a plurality of channelized resistors. The channelized resistors connected in series to either an input or an output of the power amplifier.

Radio frequency (RF) amplifier circuitry for amplifying an RF input signal to provide an RF output signal includes target envelope supply voltage compensation circuitry, envelope tracking power supply circuitry, and power amplifier circuitry. The target envelope supply voltage compensation circuitry is configured to compensate a target envelope supply voltage to provide a compensated target envelope supply voltage, which is used by the envelope tracking power supply circuitry to provide an output envelope supply voltage. The power amplifier circuitry is configured to amplify the RF input signal using a power amplifier envelope supply voltage. The power amplifier envelope supply voltage is different from the output envelope supply voltage due to a parasitic impedance. The target envelope supply voltage compensation circuitry is configured to compensate the target envelope supply voltage to reduce an error between the target envelope supply voltage and the power amplifier envelope supply voltage.

Systems and methods are provided for improved noise performance of audio amplifiers. In one example, a system includes a multistage amplifier comprising at least a first stage amplifier and a second stage amplifier. The system further includes a plurality of switches disposed within the multistage amplifier to configure the multistage amplifier. The system further includes a control signal configured to control the multistage amplifier to a normal amplification mode or a mute state, wherein the multistage amplifier is adapted to amplify an input signal in the normal amplification mode, the multistage amplifier is adapted to output a zero signal in the mute state, and internal amplification stages of the multistage amplifier are disabled in the mute state, and output stages of each of the at least first stage amplifier and the second stage amplifier are electrically shorted and/or shorted to a fixed bias voltage in the mute state.

A wideband envelope modulator comprises a direct current (DC)-to-DC switching converter connected in series with a linear amplitude modulator (LAM). The DC-DC switching converter includes a pulse-width modulator that generates a PWM signal with modulated pulse widths representing a time varying magnitude of an input envelope signal or a pulse-density modulator that generates a PDM signal with a modulated pulse density representing the time varying magnitude of the input envelope signal, a field-effect transistor (FET) driver stage that generates a PWM or PDM drive signal, a high-power output switching stage that is driven by the PWM or PDM drive signal, and an output energy storage network including a low-pass filter (LPF) of order greater than two that filters a switching voltage produced at an output switching node of the high-power output switching stage.

A communication circuit, including a first supply modulator configured to provide a first supply voltage; a first power amplifier configured to generate a first output signal by amplifying a first input signal corresponding to a first operation frequency band, a second power amplifier configured to generate a second output signal by amplifying a second input signal corresponding to a second operation frequency band; and a switching circuit configured to selectively provide the first supply voltage from the first supply modulator to the second power amplifier based on a first switching signal according to an operation node.

A multi-mode envelope tracking (ET) target voltage circuit is provided. In an ET amplifier apparatus, an amplifier circuit is configured to amplify a radio frequency (RF) signal based on a time-variant ET voltage, which is generated based on a time-variant ET target voltage configured to track a time-variant power envelope of the RF signal. Notably, when the ET amplifier apparatus operates in a fifth-generation (5G) standalone (SA) or non-standalone (NSA) mode, the amplifier circuit may experience interference creating a reverse intermodulation product (rIMD) that can degrade efficiency and performance of the amplifier circuit. In examples discussed herein, the multi-mode ET target voltage circuit is configured to generate the ET target voltage based on a reduced slew rate to help suppress the rIMD at the amplifier circuit, thus making it possible to improve efficiency and performance of the ET amplifier apparatus in the SA and the NSA modes.

An envelope stacking power amplifier system reduces current for a given output power level without sacrificing the ability to support large voltage swings at saturation and therefore increases efficiency at the maximum linear operating power and all power levels below that. The system includes a stack/unstack controller including circuitry configured to switch the RF power amplifier system between a stacked mode in which first and second RF amplifiers are coupled in a stacked configuration and an unstacked mode in which the first and second RF amplifiers are coupled in an unstacked configuration in response to one or more mode-control signals, the stacked configuration providing reduced current compared to the unstacked configuration.

A distributed envelope tracking (ET) amplifier circuit and related apparatus are provided. The distributed ET amplifier apparatus includes an amplifier circuit configured to amplify a radio frequency (RF) signal based on a modulated voltage. In examples discussed herein, the amplifier circuit is co-located with an ET voltage circuit configured to supply the modulated voltage such that a trace inductance between the amplifier circuit and the ET voltage circuit can be reduced to below a defined threshold. By co-locating the amplifier circuit with the ET voltage circuit to reduce a coupling distance between the amplifier circuit and the ET voltage circuit and thus the trace inductance associated with the coupling distance, it may be possible to reduce degradation in the modulated voltage. As a result, it may be possible to improve efficiency and maintain linearity in the amplifier circuit, particularly when the RF signal is modulated at a higher modulation bandwidth.

A speaker excursion characterizing system for a speaker includes a signal generator configured to generate a signal at a plurality of different amplitudes. The signal may be generated at a plurality of frequencies. An inverse excursion filter has an inverse excursion filter response, receives the signal and applies the inverse excursion filter response and has an output in communication with an amplifier circuit of the speaker. The inverse excursion filter response is an inverse of an excursion filter response of an excursion filter in the amplifier circuit of the speaker.