A radio frequency (RF) equalizer in an envelope tracking (ET) circuit is disclosed. A transmitter chain includes an ET circuit having an RF equalizer therein. The RF equalizer includes a two operational amplifier (op-amp) structure that provides a relatively flat gain and a relatively constant negative group delay across a frequency range of interest (e.g., up to 200 MHz). The simple two op-amp structure provides frequency response equalization and time tuning adjustment and/or creates a window Vcc signal.

Apparatus and methods for power amplifier signal limiting are disclosed. In certain embodiments, a power amplifier system includes a power amplifier that amplifies a radio frequency input signal, and a signal limiter operable to limit a signal power of the power amplifier when the radio frequency input signal exceeds a threshold. The signal limiter includes a radio frequency detector configured to generate a detection signal based on detecting a power level of the radio frequency input signal, and a latch configured to lock the signal limiter into an attenuating mode in response to the detection signal indicating that the threshold is exceeded.

An audio system has an amplifier for driving an audio actuator and includes a switched-mode power supply that draws power from a power source (e.g., battery) to supply power to the amplifier, a capacitor charged by the switched-mode power supply to supply power to the amplifier, and a feed-forward compressor that performs dynamic range compression of an audio input to provide an audio output for amplification by the amplifier. The compressor includes a sidechain frequency-biasing filter that generates a frequency-biased version of the audio input that is attenuated as frequency increases which causes the compressor to decrease the compression as frequency increases. A control block limits current drawn from the battery by the switched-mode power supply independent of audio input frequency, but the frequency-biasing filter enables the amplifier to service audio power transients greater than the current-limited power supply can supply by advantageously concurrently sourcing extra power from the capacitor.

An amplification device includes an amplification unit, an impedance unit and a log power detector. The amplification unit includes an input terminal for receiving a radio-frequency signal, an output terminal for outputting an amplified radio-frequency signal, and a detected terminal for outputting a detected signal related to the radio-frequency signal. The impedance unit is used to provide an impedance. The impedance unit includes an input terminal coupled to the detected terminal of the amplification unit for receiving the detected signal, and an output terminal for outputting a power signal. The log power detector is used to generate a power indication signal according to the power signal. The log power detector includes an input terminal coupled to the output terminal of the impedance unit, and an output terminal for outputting the power indication signal.

Envelope tracking systems for power amplifiers are provided herein. In certain embodiments, an envelope tracker is provided for a power amplifier that amplifies an RF signal. The envelope tracker includes a multi-level switching circuit having an output that provides an output current that changes in relation to an envelope signal indicating an envelope of the RF signal when the envelope tracker is operating in an envelope tracking mode. The multi-level switching circuit includes a multi-level supply (MLS) modulator that receives multiple regulated voltages of different voltage levels, and an MLS control circuit that controls the selection of the MLS modulator over time based on the envelope signal. When transitioning the MLS modulator from selection of one regulated voltage level to another regulated voltage level, the MLS control circuit provides a soft transition to gradually switch the regulated voltage levels.

A near-field transmitter includes a power amplifier, a resonant network, an envelope detector, and an antenna tuning circuit. The power amplifier has an input for receiving a communication signal, and an output for providing a differential output signal. The resonant network is coupled to the output of the power amplifier and has a tunable reactive element tuned by a tuning signal. The envelope detector is coupled to the output of the power amplifier for providing an envelope signal in response to the differential output signal. The antenna tuning circuit is for adjusting the tuning signal in response to the envelope signal.

A distributed power management circuit is disclosed. Herein, a phase correction in a radio frequency (RF) signal is performed by a power management integrated circuit (PMIC), a distributed PMC, and a power amplifier circuit. The power amplifier circuit includes a phase shifter circuit configured to phase-shift the RF signal based on a phase correction signal and a power amplifier configured to amplify the phase-shifted RF signal based on a modulated voltage. The distributed PMIC is configured to generate the phase correction signal and the modulated voltage based on a modulated target voltage. The PMIC is configured to generate the modulated target voltage based on a time-variant power envelope of the RF signal. As a result, the modulated voltage and the time-variant power envelope can be better aligned in time and/or phase at the power amplifier circuit to thereby improve efficiency and linearity of the power amplifier.

A power amplifier circuit supporting phase correction in a radio frequency (RF) signal is disclosed. The power amplifier circuit includes a power amplifier configured to amplify an RF signal based on a modulated voltage. The power amplifier circuit also includes a phase correction circuit configured to generate a phase correction signal based on the modulated voltage to thereby cause a phase change in the RF signal before the RF signal is amplified by the power amplifier. As a result, the modulated voltage and the time-variant power envelope can be better aligned in time and/or phase at the power amplifier circuit to thereby improve efficiency and linearity of the power amplifier circuit.

According to various embodiments, an electronic device may include: a communication processor, a radio frequency (RF) integrated circuit (RFIC) configured to receive a signal output from the communication processor and to modulate the signal into an RF signal, a power management circuit, a first power amplifier configured to amplify an RF signal output from the RFIC based on power supplied from the power management circuit, a second power amplifier configured to amplify the RF signal output from the RFIC based on the power supplied from the power management circuit, at least one capacitor connected in parallel to a power supply terminal of the first power amplifier, and at least one switch connected between the power supply terminal and the at least one capacitor, wherein the communication processor is configured to: identify a power amplification mode based a frequency band of the RF signal, and control the at least one switch by outputting a control signal corresponding to the identified power amplification mode.

An envelope tracking method and device are provided. The envelope tracking method includes: acquiring, by a boost circuit, a target envelope tracking input current signal, and transmitting, by the boost circuit, the target envelope tracking input current signal to an amplifier circuit, where the amplifier circuit includes an operational amplifier and a feedback network, and the operational amplifier operates in a mode of floating ground; and performing, by the amplifier circuit, closed-loop conversion and amplification on the target envelope tracking input current signal and outputting, by the amplifier circuit, an envelope tracking output voltage.