A power amplifier circuit includes a power amplifier including a first transistor having a first terminal connected to a reference potential, a second terminal to which a first current and a radio-frequency signal are input, and a third terminal connected to a first power supply potential via a first inductor; a capacitor connected to the third terminal of the first transistor; a second transistor including a first terminal connected to the capacitor and the reference potential via a second inductor, a second terminal to which a second current is input and is connected to the reference potential, and a third terminal connected to the first power supply potential via a third inductor and outputs signal; and an adjustment circuit that outputs a third current corresponding to the first power supply potential or a second power supply potential to the second terminal of the second transistor.

A multi-frequency low noise amplifier includes an input matching network, an amplifying circuit and an output matching network. The input matching network includes a first out-of-band rejection circuit and a first frequency band selection circuit. The output matching network includes a second out-of-band rejection circuit and a second frequency band selection circuit. The first out-of-band rejection circuit can reject signal of any frequency band in the radio frequency signals so that signals of the remaining frequency bands can pass through. The first frequency band selection circuit can screen out the signals of reference frequency spots from the remaining frequency bands. The second frequency band selection circuit can screen out the signals of partial frequency spots from the amplified signals of reference frequency spots. The second out-of-band rejection circuit can reject the signal of any frequency spot in the signals of partial frequency spots.

Amplifier circuits, radio communication circuits, radio communication devices, and methods provided in this disclosure provide an amplifier circuit. The amplifier circuit may include an amplifier configured to amplify an input signal to provide an output signal. The amplifier circuit may further include an amplifier stack including a first transistor coupled to the amplifier. The amplifier stack may be configured to receive the output signal to amplify the output signal. The amplifier stack may be configured to receive an input control signal to control the first transistor based on an envelope of the input signal.

An amplifier circuit includes a first amplifier that amplifies a high frequency signal, and a load circuit that changes a load impedance of the first amplifier without being controlled by an external circuit so that a saturation power at a first temperature is higher than a saturation power at a second temperature lower than the first temperature, and an efficiency at the first temperature is lower than an efficiency at the second temperature.

An RF transceiver front end includes a receiver limb including a length of transmission line, an impedance matching network, a downstream shunt switch and a downstream further receiver component and a transmitter limb. The impedance matching network is configured to transform the input impedance of the further receiver component to match the input impedance of the receiver limb when the shunt switch is open and the RF transceiver front end is operable in receiver mode. The impedance matching network is further configured to transform the input impedance of the shunt switch to present an open circuit as the input impedance of the receiver limb when the shunt switch is closed and the RF transceiver front end is operable in transmitter mode. The length of transmission line can be from zero to less than λ/4 at the operating frequency of the RF transceiver.

A harmonic processing circuit includes a first inductor having a first end connected to a connection line connected between an amplifier and an impedance matching circuit, and a second end connected to a first node, a first transmission line having a third end connected to the first node and a fourth end connected to a second node, and a parallel resonant circuit having a fifth end connected to the second node and a sixth end connected to a reference potential, wherein a second inductor and a first capacitor are connected in parallel between the fifth end and the sixth end, wherein when the first inductor is viewed from the connection line, an impedance at a frequency of a fundamental wave amplified by the amplifier is larger than an impedance at a frequency of a second harmonic having twice the frequency of the fundamental wave.

An apparatus includes a transformer including a first inductor, a second inductor, and a third inductor. The apparatus also includes a power amplifier having an output coupled to the first inductor, a low-noise amplifier having an input coupled to a first terminal of the third inductor, and a fourth inductor having a first terminal and a second terminal, wherein the second terminal of the fourth inductor is coupled to a second terminal of the third inductor. The apparatus also includes a switch coupled between the first terminal of the third inductor and the first terminal of the fourth inductor.

Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores in a particular gain mode to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a low noise figure amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity. The disclosed signal amplifiers can switch between a first active core and a second active core for a single or particular gain mode to achieve desired signal characteristics during different time periods.

A device for controlling wireless charging output power based on a PWM integrating circuit includes a magnetic-resonance transmitting module and a magnetic-resonance receiving module. The magnetic-resonance transmitting module includes a wireless charging base, a Bluetooth master circuit, a DC/DC regulator circuit, a PWM integrating circuit, a radio-frequency power amplifier source, a radio-frequency current sampling circuit and a magnetic-resonance transmitting antenna. Both the radio-frequency power amplifier source and the magnetic-resonance transmitting antenna are mounted at the wireless charging base. The magnetic-resonance transmitting antenna is connected to the magnetic-resonance receiving module. The magnetic-resonance receiving module includes a cooling fin, a magnetic-resonance receiving antenna, a Bluetooth slave circuit, a receiving rectifier and regulator circuit and a charging control circuit. The magnetic-resonance receiving antenna, the receiving rectifier and regulator circuit and the charging control circuit are connected successively. The magnetic-resonance receiving antenna is arranged directly above the magnetic-resonance transmitting antenna.

A packaged RF transistor amplifier includes an RF transistor amplifier die having a first terminal, a first lead, an integrated passive device that includes a first series microstrip transmission line, a first bond wire coupled between the first terminal and the first series microstrip transmission line, and a second bond wire coupled between the first series microstrip transmission line and the first lead.