A front end module (FEM) and associated method for receiving signals in a front end module are disclosed. Some embodiments of the FEM have three inputs. The FEM can process the input signals in one of three bypass modes. In bypass modes, switchable tank circuits provide a high impedance to isolate active components from the bypass path. This improves the input return loss in the passive bypass mode and thus improves the performance of the passive bypass mode by allowing the use of LNAs without an input switch. In the active gain mode, one of a plurality of signals are amplified by one of an equal number of amplifiers coupled to the FEM output. Accordingly, the FEM can output signals applied to any one of the FEM inputs in bypass mode, or an amplified version of one of the input signals. In some embodiments, the FEM has only one input and one LNA. In such embodiments, an output selector switch selects between a bypass path and a gain path.

A power amplifier circuit includes: a first differential amplifier that amplifies a first signal split from the input signal and outputs a second signal; a second differential amplifier that amplifies a third signal split from the input signal and outputs a fourth signal; a first transformer including a first input-side winding to which the second signal is input and a first output-side winding; a second transformer including a second input-side winding to which the fourth signal is input and a second output-side winding; a first phase conversion element that is connected in parallel with the first output-side winding and outputs a fifth signal; and a second phase conversion element that is connected in parallel with the second output-side winding and outputs a sixth signal. The first and second output-side windings are connected in series and output a signal obtained by adding voltages of the fifth and sixth signals together.

Aspects of this disclosure relate to a multi-mode power amplifier system. A first power amplifier is configured to provide a radio frequency signal associated with a different radio access technology in a first mode than in a second mode. A second power amplifier is configured to be active in the first mode such that the first power amplifier and the second power amplifier are concurrently active in the first mode. A switch can electrically connect the output of the first power amplifier to different radio frequency signal path in the first mode than in the second mode. Related methods, power amplifier modules, and wireless communication devices are disclosed.

Power amplification system is disclosed. A power amplification system can include a Class-E push-pull amplifier including a transformer balun. The power amplification can further include a reactance compensation circuit coupled to the transformer balun. In some embodiments, the reactance compensation circuit is configured to reduce variation over frequency of a fundamental load impedance of the power amplification system.

Power amplification system is disclosed. A power amplification system can include a Class-E push-pull amplifier including a transformer balun. The power amplification can further include a reactance compensation circuit coupled to the transformer balun. In some embodiments, the reactance compensation circuit is configured to reduce variation over frequency of a fundamental load impedance of the power amplification system.

Power amplification system is disclosed. A power amplification system can include a Class-E push-pull amplifier including a transformer balun. The power amplification can further include a reactance compensation circuit coupled to the transformer balun. In some embodiments, the reactance compensation circuit is configured to reduce variation over frequency of a fundamental load impedance of the power amplification system.

Power amplification system is disclosed. A power amplification system can include a Class-E push-pull amplifier including a transformer balun. The power amplification can further include a reactance compensation circuit coupled to the transformer balun. In some embodiments, the reactance compensation circuit is configured to reduce variation over frequency of a fundamental load impedance of the power amplification system.

A Wilkinson power divider includes: -type LPFs connected to an input terminal; a T-type HPF having one end connected to one of the -type LPFs and having another end connected to a carrier amplifier; another T-type HPF having one end connected to another one of the -type LPFs and having another end connected to a /4 line; and an isolation resistor connected to connection points.

A Wilkinson power divider includes: -type LPFs connected to an input terminal; a T-type HPF having one end connected to one of the -type LPFs and having another end connected to a carrier amplifier; another T-type HPF having one end connected to another one of the -type LPFs and having another end connected to a /4 line; and an isolation resistor connected to connection points.

A method, system and apparatus provide operation of an RF amplifier at a power level responsive to detected or expected conditions such as weather attenuation.