Abstract: A balun includes: first wiring that has a first end connected to a first balanced line and a second end connected to a second balanced line; second wiring that has a grounded first end and a second end; third wiring that has a first end connected to the second end of the second wiring and a second end connected to an unbalanced line and is electromagnetically coupled to the second wiring; a first capacitor that has a first end connected to the first end of the third wiring and a grounded second end; and a second capacitor that has a first end connected to the second end of the third wiring and a grounded second end. The first wiring is electromagnetically coupled to at least one of the second wiring and the third wiring.

Abstract: A power amplifier circuit includes a first amplifier that amplifies a first signal that is one of balanced signals and outputs a first amplified signal from a first output terminal, a second amplifier that amplifies a second signal that is another of the balanced signals and outputs a second amplified signal from a second output terminal, a balun that generates a third signal from the first amplified signal and the second amplified signal, and a matching circuit that is provided between the first amplifier and the second amplifier, and the balun.

Abstract: A first resonant circuit and a second resonant circuit are included, the first resonant circuit includes a first inductance element and a first capacitor, the second resonant circuit includes a second inductance element and a second capacitor, one end portion of the first inductance element is connected to an output terminal of an amplifier, another end portion of the first inductance element is connected to one end portion of the second inductance element and one end portion of the first capacitor, and another end portion of the second inductance element is connected to the power source and one end portion of the second capacitor.

Abstract: A power amplification circuit includes a first amplifier that amplifies a signal split from an input signal, a second amplifier that amplifies a signal having a different phase from the aforementioned signal, third and fourth amplifiers, and a matching network. The matching network includes a first wiring having a first end connected to an output terminal of the first amplifier and a second end connected to an input terminal of the third amplifier, a second wiring having a first end connected to the input terminal of the third amplifier, and electromagnetically coupled to the first wiring, a third wiring having a first end connected to an output terminal of the second amplifier and a second end connected to an input terminal of the fourth amplifier, and a fourth wiring having a first end connected to the input terminal of the fourth amplifier, and electromagnetically coupled to the third wiring.

Abstract: A power amplifier circuit includes a power supply terminal and an amplifier transistor that has a base terminal, a collector terminal connected to the power supply terminal, and an emitter terminal and that performs power amplification of a radio-frequency input signal input through the base terminal to output a radio-frequency signal subjected to the power amplification from the collector terminal. The amplifier transistor receives first bias current via the base terminal assuming a first power supply voltage is applied to the power supply terminal and receives second bias current smaller than the first bias current via the base terminal assuming a second power supply voltage higher than the first power supply voltage is applied to the power supply terminal.

Abstract: A power amplifier circuit includes a first amplifier, a second amplifier, and, an output terminal. The power amplifier circuit includes an impedance conversion unit connected to an output end of one amplifier, which is either the first amplifier or the second amplifier. The impedance conversion unit includes a first line with one end connected to the output end, a second line with one end connected to another end of the first line, and a first capacitor with one end connected to a connection point between the first line and the second line and with another end connected to a reference potential. The first line and the second line are coupled to each other. A signal based on a connection point between an output end of another amplifier of the first amplifier and the second amplifier and another end of the second line is outputted from the output terminal.

Abstract: A power amplifier circuit includes: a first amplifier; a second amplifier; and an impedance inverter that delays an output of the first amplifier by a time equivalent to ¼ of a wavelength of a transmission line, and combines the output of the first amplifier delayed by the impedance inverter and an output of the second amplifier and outputs a combined output. The impedance inverter includes a plurality of unit circuits each constituted by an inductor and a capacitor, the plurality of unit circuits are cascade-connected to an output side of the first amplifier, an element included in each unit circuit of the plurality of unit circuits is connected in series to the element of an adjacent unit circuit, and another element included in each unit circuit of the plurality of unit circuits is connected between one end of the element of the same unit circuit.

Abstract: A bias circuit includes: a first transistor having an emitter or a source which supplies a bias to an amplifier operating by a power source voltage through a first resistive element and a base or a gate; a first capacitor having a first end electrically connected to the base or the gate of the first transistor and a second end connected to a ground; and a second transistor having a collector or a drain electrically connected to the base or the gate of the first transistor, a base or a gate electrically connected to the base or the gate of the first transistor, and an emitter or a source connected to a node which is supplied with a signal with experience of being amplified by the amplifier and the power source voltage.

Abstract: A differential amplifier circuit includes a first and second amplifiers that output a differential signal in a radio-frequency band, a first inductor having a first end connected to an output end of the first amplifier, a second inductor having a first end connected to an output end of the second amplifier, a choke inductor connected to second ends of the first and second inductors, a first and second capacitors, and a switch that connects the second capacitor in parallel to the first capacitor or terminates a parallel connection of the first and second capacitors. A resonant circuit formed by connecting the first or second inductor in series with the first capacitor has a different resonant frequency from a resonant circuit formed by connecting the first or second inductor in series with the parallel-connected first and second capacitors. These resonant frequencies correspond to second harmonic frequencies of the differential signal.

Abstract: A power amplifier circuit has an input node from which an input signal, which is a high-frequency signal, is inputted and an output node to which the input signal is amplified by a differential amplifier circuit to be outputted as an output signal. The power amplifier circuit includes a balun transformer (second balun transformer) including an input-side winding that has a substantially center to which a power-supply voltage is supplied and that is connected between differential outputs of the differential amplifier circuit, and an output-side winding that is coupled to the input-side winding via an electromagnetic field and that has one end connected to a reference potential; and a capacitive element (capacitor) provided between another end (node) of the output-side winding and the output node.

Abstract: A power amplifier circuit includes a first amplifier that operates in accordance with a first voltage supplied from a voltage supply source, amplifies a first signal, and outputs an amplification signal, a bias transistor that includes a base or a gate to which a bias control current is supplied and an emitter or a source supplying a bias to the first amplifier through a first resistor element, and a protection circuit that causes part of the bias control current to flow to a ground on the basis of the amplification signal and a second signal based on the first voltage.

Abstract: A power amplifier circuit includes a first amplification element having an output terminal and amplifying a harmonic signal input to an input terminal, a second amplification element having an output terminal and amplifying a harmonic signal input to an input terminal, a bias circuit that supplies a bias to each of the input terminal of the first amplification element and the second amplification element, a first resistance element electrically connected to the output terminal of the first amplification element, and a second resistance element electrically connected to the output terminal of the second amplification element and electrically connected to the other end of the first resistance element in series, the bias circuit is electrically connected to a connection point in a portion in which the other end of the first resistance element and the other end of the second resistance element are electrically connected in series.

Abstract: A power amplifier circuit includes a power splitter, a first amplifier configured to output a first amplified signal from a first output terminal, and a second amplifier configured to output a second amplified signal from a second output terminal. The power amplifier circuit further includes a first termination circuit connected between the first output terminal and the second output terminal, a first transmission line, a second transmission line, a second termination circuit connected between another end of the first transmission line and another end of the second transmission line, and a power combiner.

Abstract: A power amplifier circuit includes a first transistor configured to receive a first signal at a base, amplify the first signal, and output a second signal from a collector; and a bias circuit configured to supply a bias current to the base of the first transistor. The bias circuit includes a second transistor configured to supply a bias current to the base of the first transistor, a third transistor including a base connected to a base of the second transistor and a collector connected to a collector of the second transistor, and a fourth transistor including a base connected to an emitter of the third transistor and a collector connected to an emitter of the second transistor and configured to draw at least part of the bias current.

Abstract: A matching circuit includes: a first wire having one end connected to a first terminal and another end; a second wire having one end connected to the other end of the first wire and another end connected to a first reference potential and electromagnetically coupled to the first wire; and a third wire having one end connected to the one end of the second wire and another end connected to a second terminal and electromagnetically coupled to at least one of the first wire and the second wire.

Abstract: A power amplifier circuit includes an amplifier transistor having a base, a collector, a bias circuit, and a first resistance element connected between the base of the amplifier transistor and the bias circuit. The bias circuit includes a voltage generation circuit, a first transistor having a base to which a first direct-current voltage is supplied, and an emitter from which the bias current or voltage is supplied, a second transistor having a base to which a second direct-current voltage is supplied, and an emitter connected to the emitter of the first transistor, a signal supply circuit disposed between the base of the amplifier transistor and the base of the second transistor, and an impedance circuit disposed between the base of the first transistor and the base of the second transistor.

Abstract: A balun includes: first wiring that has a first end connected to a first balanced line and a second end connected to a second balanced line; second wiring that has a grounded first end and a second end; third wiring that has a first end connected to the second end of the second wiring and a second end connected to an unbalanced line and is electromagnetically coupled to the second wiring; a first capacitor that has a first end connected to the first end of the third wiring and a grounded second end; and a second capacitor that has a first end connected to the second end of the third wiring and a grounded second end. The first wiring is electromagnetically coupled to at least one of the second wiring and the third wiring.

Abstract: The present disclosure provides a power amplifier circuit capable of suppressing the occurrence of noises while enabling control of an output power level. The power amplifier circuit includes a first transistor that amplifies a first signal; a bias circuit that supplies a bias current or voltage based on a control signal to the first transistor; a second transistor to which a control current based on the control signal is supplied, which has an emitter or a source thereof connected to a collector or a drain of the first transistor, and from which a second signal obtained by amplifying the first signal is output; and a first feedback circuit provided between the collector or the drain of the second transistor and the base or the gate of the second transistor.

Abstract: A power amplifier circuit includes an amplifier transistor, a bias circuit that supplies a bias current or voltage to the amplifier transistor, and a resistance element connected between a base of the amplifier transistor and the bias circuit. The bias circuit includes a voltage generation circuit, a first transistor having a base to which a first direct-current voltage is supplied and an emitter from which the bias current or voltage is supplied, a second transistor having a base to which a second direct-current voltage is supplied and an emitter connected to the emitter of the first transistor, a signal supply circuit that supplies an input signal to the base of the second transistor, and an impedance circuit disposed between the base of the first transistor and the base of the second transistor.

Abstract: A power amplifier includes power amplification circuits in a plurality of stages including a first stage and a second stage, each power amplification circuit including a transistor. The power amplification circuit in the first stage includes a first impedance circuit between an emitter of the transistor and a reference potential. The first impedance circuit has an impedance that does not vary with frequency or an impedance that varies with frequency. The power amplification circuit in the second stage includes a second impedance circuit between an emitter of the transistor and a reference potential. The second impedance circuit has an impedance that does not vary with frequency or an impedance that varies with frequency.