A method for improving circuit stability is disclosed. In the method of the present invention, the circuit is analyzed to find the frequency band in which the input impedance at a target node behaves as a negative resistance, and then find the signal path of the frequency band in the matching circuit in front of the target node and add an attenuator in the signal path. This prevents the circuit from oscillation and improves the stability of the circuit. Furthermore, the signal on the main signal path will not be attenuated and the performance of the circuit will be maintained.

A communication device includes a power amplifier that generates power signals according to one or more operating bands of communication data, with the amplitude being driven and generated in output stages of the power amplifier. The final stage can include an output passive network that suppresses suppress an amplitude modulation-to-phase modulation (AM-PM) distortion. During a back-off power mode a bias of a capacitive unit of the output power network component can be adjusted to minimize an overall capacitance variation. A output passive network can further generate a flat-phase response between dual resonances of operation.

Disclosed in the present invention are a balanced radio frequency power amplifier, a chip and a communication terminal. The radio frequency power amplifier divides, by means of a 90-degree power splitter unit, a radio frequency input signal into two equal-amplitude signals having a phase difference of 90 degrees, the two radio frequency input signals are amplified and then inputted into an adjustable 90-degree power combiner, and the values of a adjustable capacitor and an adjustable resistor in the adjustable 90-degree power combiner are controlled by means of a control unit, so as to synthesize the two radio frequency input signals into one radio frequency input signal when the phase difference and amplitude difference of the two signals at different frequencies are the smallest, and to input the radio frequency input signal into a circuit of the next stage by means of a specific radio frequency transmission path.

A digital power amplifier comprising at least two individually activatable amplifiers connected to an output network comprising a first hybrid coupler. An output of a first amplifier is connected to a first input of the first hybrid coupler and an output of a second amplifier is connected to a second input of the first hybrid coupler such that activating an amplifier of the at least two amplifiers causes the amplifier to load modulate another activated amplifier of at least two amplifiers.

A power amplifier circuit includes power amplifiers connected in stages to amplify a high-frequency input signal and to output an amplified high-frequency output signal, bias circuits each of which outputs a bias current to a corresponding one of the power amplifiers, and a bias control circuit configured to output a bias control current based on a second reference potential that varies in response to power of the high-frequency output signal and that is a potential of a portion in one bias circuit of the bias circuits to one or more bias circuits in a stage preceding the one bias circuit for increasing a bias current outputted from the one or more bias circuits in the stage preceding the one bias circuit.

Front-end for processing 2G signal using 3G/4G paths. In some embodiments, a front-end architecture can include a first amplification path and a second amplification path, with each being configured to amplify a 3G/4G signal, and the first amplification path including a phase shifting circuit. The front-end architecture can further include a splitter configured to receive a 2G signal and split the 2G signal into the first and second amplification paths, and a combiner configured to combine amplified 2G signals from the first and second amplification paths into a common output path. The front-end architecture can further include an impedance transformer implemented along the common output path to provide a desired impedance for the combined 2G signal.

A power splitter that amplifies an input radio-frequency (RF) signal. The power splitter uses a single transistor in a common emitter stage of a cascode amplifier and two or more common base stages of the cascode amplifier to amplify and to split the input RF signal. A common base biasing signal can be used to simultaneously enable two or more of the common base stages to generate two or more amplified RF output signals.

A power amplifier includes a power splitter that splits a first signal into a second signal and a third signal, a first amplifier that amplifies the second signal within an area where the first signal has a power level greater than or equal to a first level and that outputs a fourth signal, a second amplifier that amplifies the third signal within an area where the first signal has a power level greater than or equal to a second level higher than the first level and that outputs a fifth signal, an output unit that outputs an amplified signal of the first signal, a first and a second LC parallel resonant circuit, and a choke inductor having an end to which a power supply voltage is supplied and another end connected to a node of the first and second LC parallel resonant circuits.

One example includes a device that is comprised of a pre-power amplifier, a power amplifier, a signal path, and a dynamic bias circuit. The pre-power amplifier amplifies an input signal and outputs a first amplified signal. The power amplifier receives the first amplified signal and amplifies the first amplified signal based on a dynamic bias signal to produce a second amplified signal at an output thereof. The signal path is coupled between an output of the pre-power amplifier and an input of the power amplifier. The dynamic bias circuit monitors the first amplified signal, generates the dynamic bias signal, and outputs the dynamic bias into the signal path.

Apparatus and methods for a no-load-modulation power amplifier are described. No-load-modulation power amplifiers can comprise multiple amplifiers connected in parallel to amplify a signal that has been divided into parallel circuit branches. One of the amplifiers can operate as a main amplifier in a first amplification class and the remaining amplifiers can operate as peaking amplifiers in a second amplification class. The main amplifier can see essentially no modulation of its load between the power amplifier's fully-on and fully backed-off states. The power amplifiers can operate in symmetric and asymmetric modes. Improvements in bandwidth and drain efficiency over conventional Doherty amplifiers are obtained. Further improvements can be obtained by combining signals from the amplifiers with hybrid couplers.