An inverted group delay circuit is provided. The inverted group delay circuit can offset a group delay between a pair of signals. In a non-limiting example, the inverted group delay circuit can be configured to offset a group delay (e.g., negative group delay) between a time-variant voltage and a time-variant envelope of an analog signal. More specifically, the inverted group delay circuit can output an inverted time-variant voltage having an opposing phase and time-adjusted relative to the time-variant voltage to thereby offset the group delay between the time-variant voltage and the time-variant envelope. As such, the inverted group delay circuit can be provided in a power management integrated circuit (PMIC) to improve timing alignment between a time-variant voltage(s) and a time-variant analog signal(s) at a power amplifier(s), thus helping to reduce potential amplitude distortion when the analog signal(s) is amplified by the power amplifier(s).

A multi-mode power management integrated circuit (PMIC) is provided. The PMIC includes a supply voltage circuit that generates a number of supply voltages based on an input voltage. The PMIC also includes a pair of voltage circuits each generating a respective voltage based on any of the supply voltages. In one operation mode, one of the voltage circuits is configured to generate an envelope tracking (ET) voltage and another one of the voltage circuits is configured to generate the input voltage for the supply voltage circuit. The input voltage may be generated according to a peak of the ET voltage to cause each of the supply voltages to be proportionally related to the peak of the ET voltage. Accordingly, the voltage circuit configured to generate the ET voltage can operate based on an appropriate one of the supply voltages, thus helping to improve efficiency and linearity of the voltage circuit.

Apparatus and methods for radio frequency (RF) signal limiting are provided. In certain embodiments, an RF signal limiting system includes a cascade of a front limiter and a biased limiter. Additionally, the front limiter provides an initial amount of limiting to an RF signal, while the biased limiter serves to further limit the RF signal. The biased limiter is adaptively biased such that the amount of limiting provided to the RF signal increases in response to an increase in the RF signal level. Such an RF signal limiting system can be used in a variety of applications, including protecting an input of a low noise amplifier (LNA).

An envelope tracking (ET) power amplifier apparatus is provided. The ET power amplifier apparatus includes an amplifier circuit configured to amplify a radio frequency (RF) signal based on an ET voltage and a tracker circuit configured to generate the ET voltage based on an ET target voltage. The ET power amplifier apparatus also includes a control circuit. The control circuit is configured to dynamically determine a voltage standing wave ratio (VSWR) change at a voltage output relative to a nominal VSWR and cause an adjustment to the ET voltage. By dynamically determining the VSWR change and adjusting the ET voltage in response to the VSWR change, the amplifier circuit can operate under a required EVM threshold across all phase angles of the RF signal.

A transmitter is provided. The transmitter includes an envelope tracking circuit, wherein the envelope tracking circuit includes an envelope circuit configured to generate, based on a baseband signal, an envelope signal indicating a temporal course of the baseband signal's envelope. Further, the envelope tracking circuit includes a bandwidth reduction circuit configured to generate a bandwidth reduced envelope signal based on the envelope signal, and a DC-to-DC converter configured to generate a supply voltage for a power amplifier of the transmitter based on the bandwidth reduced envelope signal. The transmitter additionally includes a predistortion circuit configured to generate a predistorted baseband signal based on the baseband signal and an adjustable predistortion configuration. The predistortion circuit is further configured to adjust the predistortion configuration based on the bandwidth reduced envelope signal.

Power amplifier modules with controllable envelope tracking noise filters are provided herein. In certain embodiments, an envelope tracking system includes a power amplifier module and an envelope tracker that provides the power amplifier module with a power amplifier supply voltage that changes based on an envelope of a radio frequency (RF) signal amplified by the power amplifier module. The power amplifier module includes a controllable filter that filters the power amplifier supply voltage to provide flexibility in filtering envelope tracking noise.

An envelope tracking system includes an envelope signal generator, a supply modulator coupled to the envelope signal generator, the supply modulator comprising a switching regulator path configured to provide an output voltage at an output node to a power amplifier when in an average power tracking (APT) mode, the switching regulator path configured to operate together with a linear path to provide the output voltage at the output node to the power amplifier when in an envelope tracking (ET) mode, a capacitor having a first and second terminal, the first terminal coupled to ground, a switch coupled between the output node and the second terminal of the capacitor, the switch being configured to selectively disconnect the capacitor from the output node, and a circuit coupled between the output node and the second terminal of the capacitor, the circuit comprising a bi-directional current-limiting switch, the circuit configured to charge or discharge the capacitor such that a voltage across the capacitor changes from a first voltage to a second voltage.

This application relates to an amplifier selectively operable in first or second modes. The first mode is a BTL mode with first and second output drivers (103p, 103n) both active to generate respective driving signals that vary with an input signal. The second mode is an SE mode, where the first output driver (103p) is active to generate a driving signal at and the output of the second driver (103n) is held constant. A controller (201) selectively controls the mode based on an indication of output signal amplitude. In the first mode, a ratio of magnitude of the two driving signals varies with the indication of output signal amplitude, i.e. the magnitudes of the two driving signals may vary so as to be not equal.

Techniques are described for using valley detection for supply voltage modulation in power amplifier circuits. Embodiments operate in context of a power amplifier circuit configured to be driven by a supply voltage generated by a supply modulator and to receive an amplitude-modulated (AM) signal at its input. The output of the power amplifier circuit can be fed to a valley detector that can detect a valley level corresponding to the bottom of the envelope of the AM signal. The detected valley level can be fed back to the supply modulator and compared to a constant reference. In response to the comparison, the supply modulator can vary the supply voltage to the power amplifier circuit in a manner that effectively tracking the envelope of the power amplifier circuit's output signal, thereby effectively seeking a flat valley for the output signal's envelope.

Apparatus and methods for power amplifier power management are disclosed. In certain embodiments, a mobile device includes a transceiver that generates a radio frequency signal, a front-end system including a first power amplifier module that amplifies the radio frequency signal, and a power management system including an envelope tracking power management unit that provides an envelope tracking supply voltage to the first power amplifier module, and a first average power tracking power management unit that provides an average power tracking supply voltage to the first power amplifier module. The first power amplifier module is configured to selectively switch between the envelope tracking supply voltage and the average power tracking supply voltage.