A mobile device can have a transceiver configured to generate a radio frequency signal and a power management system with envelope tracking. The device can also have a power amplifier system having a driver transistor coupled to a radio frequency signal input, a transformer balun having a main primary coil connected between the driver transistor and a voltage supply node of the power amplifier system, a secondary coil magnetically coupled to the main primary coil and an additional primary coil configured to generate a feedback signal related to a signal of the main primary coil. The power amplifier system can also have a push-pull amplifier with a first transistor having a base connected to a first end of the secondary coil and a second transistor having a base connected to a second end of the secondary coil. Accordingly, push-pull stage neutralization can deploy two transistors cross-connected to opposite ends of an output coil in a transformer balun.

A radio frequency module is provided that includes a module laminate having main surfaces that oppose each other; at least one power amplifier circuit on a first main surface; and at least one integrated circuit on the second main surface. The integrated circuit includes at least one switch included in a switched-capacitor circuit and at least one switch included in a supply modulator. The switched-capacitor circuit generates a plurality of discrete voltages based on an input voltage and outputs the generated plurality of discrete voltages to the supply modulator. The supply modulator selectively outputs at least one voltage of the generated plurality of discrete voltages to a power amplifier. The power amplifier circuit includes a first amplifying transistor of the power amplifier.

A radio frequency module is provided that includes a module laminate and first and second integrated circuits on the module laminate. The first integrated circuit includes at least one switch included in a converter circuit. The second integrated circuit includes a first amplifying transistor of a power amplifier that amplifies a radio frequency signal, and a second amplifying transistor of a low-noise amplifier that amplifies a radio frequency signal. The power amplifier is connected to an ET voltage generation circuit that generates a variable voltage based on an output voltage from the converter circuit and an envelope signal. The low-noise amplifier is connected to a constant voltage generation circuit that generates a constant voltage based on the output voltage from the converter circuit.

A radio frequency system can include: a voltage regulator configured to generate a DC voltage signal; a power amplifying module configured to receive an input radio frequency signal, the DC voltage signal as a supply voltage, and to generate an amplified voltage signal by amplifying the input radio frequency signal; and a controller configured to regulate the DC voltage signal in accordance with a reference signal representing the input radio frequency signal, in order to decrease a power loss of the power amplifying module.

An envelope stacking power amplifier system reduces current for a given output power level without sacrificing the ability to support large voltage swings at saturation and therefore increases efficiency at the maximum linear operating power and all power levels below that. The system includes a stack/unstack controller including circuitry configured to switch the RF power amplifier system between a stacked mode in which first and second RF amplifiers are coupled in a stacked configuration and an unstacked mode in which the first and second RF amplifiers are coupled in an unstacked configuration in response to one or more mode-control signals, the stacked configuration providing reduced current compared to the unstacked configuration.

An envelope tracking system has an envelope tracker that is configured to generate a power amplifier supply voltage that changes is relation to an envelope of a radio frequency signal, and a power amplifier comprises at least a first amplification stage having an input terminal receiving a radio frequency (RF) signal to be amplified. The power amplifier has a first coupling unit, and a second coupling unit inductively coupled with the first coupling unit, the second coupling unit provides radio frequency-coupled feedback to the input terminal of the first amplification stage through a radio frequency-coupled feedback path.

Apparatus and methods for biasing power amplifiers are provided herein. In certain embodiments, a power amplifier includes a bipolar transistor having a base biased by a bias network having a reactance that controls an impedance at the transistor base to achieve substantially flat phase response over large dynamic power levels. For example, the bias network can have a frequency response, such as a high-pass or band-pass response, that reduces the impact of power level on phase distortion (AM/PM).

The present invention relates to a differential envelope detector, which comprises: input terminals for separating cathode and anode components from a signal and receiving same; a first voltage output unit for outputting a first common mode voltage between the input terminals; a first amplification unit, which receives an input signal as a differential pair and amplifies same so as to output a first output signal; a second amplification unit, which receives the first common mode voltage so as to output a second output signal; and a second voltage output unit for outputting a second common mode voltage between a constant current source unit and an output terminal, wherein the output size of the detector is hardly affected by temperature changes, and an output DC voltage is also fixed so as to be effective with respect to input bias of the next stage amplifier.

In some embodiments, a hybrid generator/modulator comprises: a regulation stage having a single input and at least two outputs, the regulation stage configured to receive an input voltage at the single input and to provide two intermediate voltages at respective ones of the at least two outputs; and a multilevel converter configured to receive the two intermediate voltages and provide an output voltage having a voltage level corresponding to a voltage level of one of the two intermediate voltages or at least one other voltage level synthesized from the two intermediate voltages.

A radio frequency module is provided that includes first and second power amplifiers that amplify a WLAN signal in a first frequency band, a voltage generation circuit that generates multiple discrete voltages, a supply modulator connected between the power amplifier and the voltage generation circuit and selectively outputs one of the multiple discrete voltages, another supply modulator connected between the power amplifier and the voltage generation circuit and selectively outputs one of the multiple discrete voltages, and first and second integrated circuits that each include a switch of one of the supply modulators. A distance between the first power amplifier and the first integrated circuit is shorter than a distance between the first power amplifier and the second integrated circuit, and a distance between the second power amplifier and the second integrated circuit is shorter than a distance between the second power amplifier and the first integrated circuit.