Embodiments disclosed herein generally relate to power amplifier matching circuits used for matching impedance and harmonic control in a device, such as a cellular phone. In one example, a power amplifier matching circuit includes two DVCs, four inductors, a transistor, and a capacitor. Utilizing the two DVCs, the impedance matching ratio and the center frequency of the circuit are capable of adjustment as needed. Moreover, the inclusion of the two DVCs may also prevent harmonic frequencies from undesirably passing through the power amplifier matching circuit to the antenna of a cellular device. The power amplifier matching circuit may be used in conjunction with an amplifier, where the output of the amplifier is proportional to the current in the circuit.

A dual-mode envelope tracking (ET) power management circuit is provided. An ET amplifier(s) in the dual-mode ET power management circuit is capable of supporting normal-power user equipment (NPUE) mode and high-power user equipment (HPUE) mode. In the NPUE mode, the ET amplifier(s) amplifies a radio frequency (RF) signal(s) to an NPUE voltage based on a supply voltage for transmission in an NPUE output power. In the HPUE mode, the ET amplifier(s) amplifies the RF signal(s) to an HPUE voltage higher than the NPUE voltage based on a boosted supply voltage higher than the supply voltage for transmission in an HPUE output power higher than the NPUE output power. The ET amplifier(s) maintains a constant load line between the NPUE mode and the HPUE mode. By maintaining the constant load line, it is possible to maintain efficiency of the ET amplifier(s) in both the NPUE mode and the HPUE mode.

Certain aspects of the present disclosure provide methods and apparatus for dynamically managing the dead time between turning on output power stage transistors in amplifiers, such as audio amplifiers. One example method of operating an amplifier generally includes generating a drive signal based on an input signal; amplifying the drive signal by alternatively driving a first transistor and a second transistor with a time between deactivating the first transistor and activating the second transistor; and adjusting the time based on a parameter of the input signal or the drive signal, during the amplifying. For example, the parameter may include an amplitude of the input signal, a duty cycle of the drive signal, or a duty cycle of a modulated signal (e.g., a pulse-width modulated signal) generated based on the input signal. The input signal may be a digital audio input signal.

A power stabilization circuit including a first reference power supply, a second reference power supply, and a combiner circuit coupled to the first reference power supply and the second reference power supply. The first reference power supply is configured to receive a first control signal, generate a first reference signal based on the first control signal, and provide the first reference signal to a first output power supply. The second reference power supply is configured to receive a second control signal, generate a second reference signal based on the second control signal, and provide the second reference signal to a second output power supply. The combiner circuit is configured to generate a combined reference signal based on the first reference signal and the second reference signal and drive a reference load based on the combined reference signal.

A power amplifying apparatus includes a radio frequency (RF) power amplifier, a supply modulating unit, a phase shifting unit, and an envelope shaping unit. The RF power amplifier receives an input RF signal and outputs an amplified RF signal. The supply modulating unit provides the RF power amplifier with a supply voltage which varies with an original envelope of the input RF signal. The phase shifting unit receives a control signal and shifts a phase of the input RF signal to be inputted to the RF power amplifier by a shift amount which varies with the control signal. The envelope shaping unit receives the original envelope and provides the phase shifting unit with the control signal which varies with the original envelope.

The single-input single-output two-box polar behavioral model for envelope tracking power amplifiers estimates magnitude and phase of the output signal in separate paths. More specifically, the model is a two-box polar behavioral model using a complex magnitude and phase splitter that feeds a parallel combination of a generalized memory polynomial function and a memoryless polynomial function applied to the input signal's magnitude and phase, respectively. The present model is experimentally validated using a gallium nitride-based envelope tracking power amplifier driven by multi-carrier test signals.

Apparatus and methods for bias switching of power amplifiers are provided herein. In certain configurations, a power amplifier system includes a power amplifier that provides amplification to a radio frequency (RF) signal and a bias control circuit that biases the power amplifier. The power amplifier includes an amplification transistor that receives the RF signal at an input, and a first bias network and a second bias network each connected to the input. The bias control circuit includes a first switch, a first reference current source that provides the first reference current to the first bias network through the first switch, a second switch, and a second reference current source that provides the second reference current to the second bias network through the second switch.

An analog predistorter (APD) core module including a radio frequency delay module, an envelope module, and a contact matrix module. The radio frequency delay module is configured to receive a feed-forward radio frequency signal, generate multiple radio frequency delay signals with different delays according to the feed-forward radio frequency signal, and output each radio frequency delay signal to the contact matrix module. The envelope module is configured to receive the feed-forward radio frequency signal, perform envelope detection on the feed-forward radio frequency signal to obtain multiple envelope signals with different delays, and output each envelope signal to the contact matrix module. The contact matrix module is configured to receive each radio frequency delay signal, each envelope signal, and a predistortion coefficient from an exterior source, and generate a predistortion signal according to the predistortion coefficient, each radio frequency delay signal, and each envelope signal.

A multi-voltage generation circuit and related envelope tracking (ET) amplifier apparatus is provided. In one aspect, a multi-voltage generation circuit is configured to generate a number of ET target voltages based on an analog voltage signal. In another aspect, a multi-amplifier ET circuit can be configured to include a number of amplifier circuits for amplifying concurrently a radio frequency (RF) signal based on a number of ET voltages. The multi-amplifier ET circuit also includes a number of driver circuits configured to generate the ET voltages base on a number of ET target voltages. In this regard, the multi-voltage generation circuit can be provided in the multi-amplifier ET circuit to generate the ET target voltages based on the analog voltage signal that corresponds to the RF signal. In examples discussed herein, the driver circuits are co-located with the amplifier circuits to help improve efficiency and maintain linearity in the amplifier circuits.

A dual-mode average power tracking (APT) controller operates in a first mode to move the control voltage quickly without concern for ripple or ringing. When this coarse adjustment takes the control voltage to within a desired margin of a target, the controller may switch to a second mode, where the APT controller more slowly approaches the target, but has reduced ringing or ripples. The mode is changed by changing resistance and capacitance values in a loop filter within the APT circuit. In a further aspect, a pulse shaper circuit may inject a pulse to force the control voltage to change more rapidly. By switching modes in this fashion, the control voltage may quickly reach a desired target, and then remain in the second mode during a transmission time slot such that the control voltage is clean throughout.