A power amplifier system having a power amplifier stage with dynamic bias circuitry is disclosed. Also included is bias control circuitry having a compression sensor having a sensor input coupled to a RF signal output and a sensor output, wherein the compression sensor is configured to generate a gain deviation signal in response to a sensed deviation from a flat gain profile of the power amplifier stage. Further included is a bias driver that is configured to drive dynamic bias circuitry to adjust bias to the power amplifier stage to maintain the flat gain profile in response to the gain deviation signal.

Voltage ripple reduction in a power management circuit is disclosed. The power management circuit includes a power amplifier circuit configured to amplify a radio frequency (RF) signal based on a modulated voltage and an envelope tracking integrated circuit (ETIC) configured to provide the modulated voltage to the power amplifier circuit via a conductive path. Notably, an output impedance presenting at an input of the power amplifier circuit can interact with a modulated load current in the power amplifier circuit to create a voltage ripple in the modulated voltage to potentially cause an undesirable error in the RF signal. Herein, the ETIC is configured to modify the modulated voltage based on feedback of the voltage ripple in the modulated voltage. As such, it is possible to reduce the output impedance at the input of the power amplifier circuit to thereby reduce the voltage ripple in the modulated voltage.

Multi-level envelope tracking systems are disclosed. In certain embodiments, a method of envelope tracking includes amplifying a radio frequency signal using a power amplifier, supplying power to the power amplifier using a power amplifier supply voltage, generating a plurality of delay-controlled regulated voltages based on controlling a delay of a plurality of regulated voltages using a controllable delay circuit, generating a modulator output voltage at a modulator output of a modulator, providing filtering using a first filter coupled between the modulator output and the power amplifier supply voltage, and controlling activation of a plurality of switches of the modulator based on an envelope of the radio frequency signal. The plurality of switches are each coupled between the modulator output and a corresponding one of the plurality of delay-controlled regulated voltages.

A tracker circuit is provided that includes a switched-capacitor circuit configured to generate a plurality of discrete voltages based on a first input voltage; a supply modulator configured to selectively output at least one of the plurality of discrete voltages to a power amplifier; a bypass path configured to bypass the switched-capacitor circuit and the supply modulator to output the first input voltage to the power amplifier; and a switch configured to switch between a connection and a disconnection of the bypass path.

Described is a system for modulating power to one or more radio frequency (RF) amplifiers to suppress undesired output signal components, improve linearity and reduce noise. The described systems and techniques enable shaping of spectral components introduced via an amplifier bias voltage owing to transitions among bias discrete states. The systems and techniques facilitate operation of multilevel, RF amplifiers under a wider range of operating conditions. In embodiments, the system includes modulators coupled to a supply terminal port of each of the one or more amplifiers to modulate the voltage levels supplied to the one or more amplifiers. The outputs of the modulators may be combined to provide a combined signal coupled to the amplifiers. A delay circuit delays switching of at least one of the power modulators relative to other modulator, by a variable time delay. This results in suppression of undesired output signal components of the amplifier output.

The present invention provides a power amplifier system configured to receive an input audio signal to generate an output audio signal is disclosed. The power amplifier system includes a reference signal generator, a dynamic headroom generator and a DC-DC converter. The reference signal generator is configured to generate a reference signal according to the input signal. The dynamic headroom generator is configured to generate an output reference signal according to the reference signal and a change rate of a signal, wherein the signal is the reference signal, the input audio signal, or correlated with the reference signal or the input audio signal. The DC-DC converter is configured to generate a supply voltage to a power amplifier, wherein a voltage level of the supply voltage is determined according to the output reference signal, and the power amplifier is configured to generate the output audio signal according to the input audio signal.

A method of envelope detection receives an RF (radio frequency) signal comprising a first voltage and a second voltage; converts the first voltage into a first current using a first VCCS (voltage controlled current source); converts the second voltage into a second current using a second VCCS; converts a bias voltage into a third current using a third VCCS; converting an output voltage into a fourth current using a fourth VCCS; sums the first current and the second current into an input current flowing through a first internal node of a first internal voltage; sums the third current and the fourth current into a mirrored current flowing through a second internal node of a second internal voltage; uses a source follower to receive the second internal voltage and output the output voltage; and uses a current mirror to force the mirrored current to be equal to the input current.

A loadline modulation power management circuit is provided. The loadline modulation power management circuit includes a power amplifier circuit and an acoustic filter circuit. Specifically, the power amplifier circuit is configured to amplify a signal to a time-variant output power based on a modulated voltage and the acoustic filter circuit is configured to pass the amplified signal for transmission in a transmit frequency. Herein, the power amplifier circuit is further configured to dynamically modulate a loadline impedance based on the time-variant output power to prevent the modulated voltage from exceeding a maximum level, whereas the acoustic filter circuit can help reduce overall transmit loss in the amplified signal. As a result, the loadline modulation power management circuit can operate with optimal efficiency and with reduced overall transmit loss.

Some exemplary aspects of the disclosure provide a tracker circuit that includes an output switching circuit, a first voltage supply path and a filter circuit. The output switching circuit is configured to selectively output at least one of a plurality of discrete voltages. The first voltage supply path is configured to connect the output switching circuit and a first power amplifier to provide the at least one of the plurality of discrete voltages to the first power amplifier. The filter circuit is configured to be connected in shunt with the first voltage supply path, the first power amplifier is configured to amplify a first radio frequency signal of a first band with time division duplex being applied.

A transceiver circuit operable in a dynamic power range is provided. In embodiments disclosed herein, the transceiver circuit is configured to generate a radio frequency (RF) signal and a target voltage that is adapted according to a power range of the RF signal. More specifically, the transceiver circuit is configured to generate the target voltage differently when the power range of the RF signal is higher (e.g., 18 dBm) or lower (e.g., <18 dBm). By adapting the target voltage based on the power range of the RF signal, it is possible to suppress a potential voltage ripple in a modulated voltage generated according to the target voltage to thereby achieve a desired adjacent channel leakage ratio (ACLR) when the RF signal is amplified at a power amplifier circuit based on the modulated voltage.