The present invention provides a compound transmitter having power efficiency characteristics and distortion characteristics superior, over a wide band, to those of a Doherty transmitter, and having fewer elements constituting an RF circuit. The present invention is therefore provided with a compound amplifier (201) for generating a signal (z) (efficiency improving signal) obtained by the amplitude modulation of a carrier signal from an RF modulation signal (a) (main signal); power-modulating, using two power amplifiers (50, 51), a signal (S1) obtained by adding together (a) and (z), and a signal (S2) obtained by subtracting (z) from (a); and setting, as a transmitter output point, the point (p1) where the respective outputs are combined via impedance inverters (60, 61), the efficiency improving signal (z) being generated under conditions in which the size of the envelope of either (S1) or (S2) is fixed.

Disclosed herein are power amplification (PA) systems configured to amplify a signal, such as a radio-frequency signal. The PA system includes a plurality of power amplifiers that are configured to amplify a signal received at a signal input and to output the amplified signal at a signal output. The power amplifiers are configured to receive a supply voltage that is a combination of a battery voltage and an envelope tracking signal. The PA system includes a PA controller configured to control the power amplifiers based at least in part on the battery voltage or a power output of the power amplifiers. The PA controller can be configured to alter impedance matching components of the PA system to reconfigure a load line of the power amplifiers.

Techniques to improve efficiencies of power amplifiers in wireless communication devices are described herein. In one embodiment, an envelope tracking supply modulator includes a pre-amplifier having an input coupled to an envelope signal and another input coupled to a threshold voltage signal, a de-multiplexer coupled to an output of the pre-amplifier, a pulse frequency modulator having an input coupled to an output of the de-multiplexer, and a pulse width modulator having an input coupled to the output of the de-multiplexer. The de-multiplexer is configured to allow the pulse frequency modulator to modulate a switching frequency to generate a switched signal according to a slew rate of the envelope signal or allow the pulse width modulator to provide the switched signal as a current source with a constant frequency, based on a comparison result between the envelope signal and the threshold voltage signal at the pre-amplifier.

An envelope tracking power amplifier is disclosed herein. The envelope tracking power amplifier includes a multi-mode bias modulator and a power amplifier. The multi-mode bias modulator generates an envelope-modulated bias voltage from the envelope signal of an radio frequency (RF) signal whose power is to be amplified by using a linear amplifier and a switching amplifier each having varying current driving capability in response to an operation mode control signal that determines any one of low-level mode and high-level mode. The power amplifier is biased in response to the envelope-modulated bias voltage, amplifies the RF signal, and outputs the amplified RF signal to an antenna.

Embodiments of the disclosure may include a method and apparatus for improving the efficiency and extending the operation time between recharges or replacement batteries of a portable audio delivery system. The audio delivery system may include a processor, an audio processing device, a speaker, and a rechargeable power source. The audio delivery system is generally configured to generate and/or receive an audio input signal and efficiently deliver an amplified, high quality audio output signal to a user. In some embodiments of the disclosure, the audio processing device of the audio delivery system may include a switch mode power supply (SMPS), a signal delay element, an envelope detector, and a switching signal amplifier.

According to one embodiment, an amplification circuit includes an amplifier having a gain and amplifying the input signal based on the gain, and a gain control signal generator controlling the gain based on an amplitude of the input signal. The gain obtained when the amplitude of the input signal is less than a first amplitude and when the amplitude of the input signal is greater than a second amplitude is lower than the gain obtained when the amplitude of the input signal is between the first and second amplitudes or when the amplitude of the input signal is one of the first and second amplitudes. The second amplitude is greater than or equal to the first amplitude.

A dynamically biased baseband current amplifier is provided. The dynamically biased baseband current amplifier includes an input interface; a controller; a variable resistor network; an amplifier stage; a hybrid differential envelope detector and full-wave rectifier; a transconductor; a first variable transistor; a second variable transistor; a third variable transistor; and a fourth variable transistor.

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.

Current balancing techniques. In an example, a circuit includes a synchronization terminal, an error amplifier, and a clock generator. The error amplifier is configured to generate a first control voltage signal based on a reference voltage and a power converter output voltage. The clock generator is configured to produce an outgoing clock signal having an outgoing clock frequency. The circuit further includes an encoder, a frequency detector, and a decoder. The encoder is coupled to the clock generator and synchronization terminal, and configured to encode the outgoing clock signal based on the first control voltage signal to provide, at synchronization terminal, an outgoing encoded clock signal. The frequency detector is coupled to synchronization terminal and configured to derive, from an incoming encoded clock signal, an incoming clock frequency. The decoder is coupled to synchronization terminal and configured to derive, from the incoming encoded clock signal, a second control voltage signal.

The present invention breaks up the frequency bands which can be filtered by a simple low-loss band-pass or low pass filter. The second harmonic frequency is reduced by use of a non-linear clipper element which controls the driving waveform symmetry and can reduce the harmonics by as much as 5-15 db which makes the filter much simpler and allows the amplifier to remain wide-band. The output waveform from the amplifier is symmetrical or nearly symmetrical.