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.

The present disclosure is to improve the power added efficiency of a power amplifier at high output power. The power amplifier includes: a first capacitor with a radio frequency signal input to one end thereof; a first transistor whose base is connected to the other end of the first capacitor to amplify the radio frequency signal; a bias circuit for supplying bias to the base of the first transistor; and a second capacitor with one end connected to the base of the first transistor and the other end connected to the emitter of the first transistor.

An audio processing device includes a signal processing circuit, a power switch circuit, a power amplifier and a detection circuit. The signal processing circuit is configured to process an audio input to generate an audio signal. The power switch circuit is configured to generate an operating voltage. The power amplifier is coupled with the signal processing circuit and the power switch circuit, and configured to drive a load circuit by the operating voltage according to the audio signal. The detection circuit is coupled with the signal processing circuit and the power switch circuit, configured to obtain a volume value from the audio signal and compare the volume value with a first volume threshold to generate a comparison result, and configured to control, according to the comparison result, the power switch circuit to set the operating voltage to have a corresponding one of multiple voltage levels.

A compensation circuit module includes a variable resistor, a detection component and a control component. A detection end of the detection component is connected with a DC blocking capacitor of the power amplifier and is configured to detect a voltage swing of an input signal of the DC blocking capacitor. The control component is connected with the detection component and is configured to output a control signal according to the input signal detected by the detection component. The variable resistor is connected with the output end of the control component and is configured to change the resistance connected to the power amplifier according to the control signal, and the resistance of the variable resistor connected to the power amplifier is configured to constitute the feedback resistance of the power amplifier.

A lookup table calibration apparatus and method are disclosed. The lookup table calibration apparatus includes a power amplifier circuit configured to amplify a radio frequency (RF) signal having time-variant power levels based on a modulated voltage. To ensure proper alignment between the modulated voltage and the time-variant power levels, the power amplifier circuit is further configured to phase-shift the RF signal based on a modulated phase correction voltage. Specifically, the modulated voltage is generated based on a modulated voltage lookup table and the modulated phase correction voltage is generated based on a phase correction voltage lookup table. Herein, the lookup table calibration apparatus can be configured to concurrently populate and/or calibrate the modulated voltage lookup table and the phase correction voltage lookup table based on a measured gain and a measured phase of the RF signal, respectively.

A power management circuit supporting phase correction in an analog signal is disclosed. The power management circuit includes a power amplifier circuit configured to amplify an analog signal having a time-variant power envelope based on a modulated voltage. The power management circuit also includes an envelope tracking (ET) integrated circuit (ETIC) configured to generate the modulated voltage and a modulated phase correction voltage to thereby cause a phase change in the analog signal. In embodiments disclosed herein, a correlation between the time-variant power envelope, the modulated voltage, and the modulated phase correction voltage is explored to thereby allow the ETIC to generate the modulated voltage and the modulated phase correction voltage based on the time-variant power envelope. As a result, it is possible to enable good time and phase alignment between the modulated voltage and the time-variant power envelope to thereby improve efficiency and linearity of the power amplifier circuit.

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.

Time-advanced phase correction in a power amplifier circuit is disclosed. The power amplifier circuit includes a power amplifier that amplifies an analog signal, which is associated with a time-variant power envelope, based on a modulated voltage. To correct phase misalignment between the modulated voltage and the time-variant power envelope, the power amplifier circuit also includes a phase correction circuit that generates a modulated phase correction voltage based on the modulated voltage to thereby cause a phase change in the analog signal. However, the modulated phase correction voltage can lag behind the modulated voltage in time due, in part, to inherent group delay of the phase correction circuit. As such, the power amplifier circuit further includes a time advance circuit to time advance the modulated phase correction voltage to thereby realign the modulated phase correction voltage and the modulated voltage in time for an optimal phase correction in the analog signal.

A power amplifier circuit includes a first power supply terminal electrically connected to a first power amplifier; a second power supply terminal electrically connected to a second power amplifier subsequent to the first power amplifier; a first external power supply line configured to electrically connect a power supply circuit configured to output a power supply potential corresponding to an amplitude level of a high-frequency input signal and the first power supply terminal; and a second external power supply line configured to electrically connect the power supply circuit and the second power supply terminal. An inductance value of the first external power supply line is higher than an inductance value of the second external power supply line.