Abstract: An apparatus and method for performing closed-loop multiple-output control of radio frequency (RF) matching for a semiconductor wafer fabrication process is provided. An apparatus for providing signals to a station of a process chamber performs semiconductor fabrication processes. A plurality of signal generators generates signals having first and second frequencies. A measurement circuit measures a voltage standing wave ratio (VSWR). A match reflection optimizer has a reactive component configured to be adjusted responsive to an output signal from the measurement circuit.

Abstract: In a semiconductor device, when a first surface of a first member is viewed in plan, at least one switch circuit including a switch is disposed within the first surface. A second member is joined to the first surface of the first member in surface contact with the first surface. The second member includes a plurality of transistors that are made of a compound semiconductor and form a radio-frequency amplifier circuit. A first conductive protrusion protrudes from the second member on an opposite side to the first member. The first member includes a circuit element disposed between the radio-frequency amplifier circuit and the at least one switch circuit in a plan view, the circuit element not forming the switch circuit.

Abstract: A directional coupler includes a main line, a secondary line, and a variable terminator. The variable terminator includes a variable inductor. The variable inductor includes a plurality of inductors coupled in series with each other between an end portion of the secondary line and the ground and switches configured to bypass at least one inductor of the plurality of inductors.

Abstract: A matching circuit, a radio frequency front-end power amplification circuit, and a mobile communication device are provided. The matching circuit is configurable for the radio frequency front-end power amplification circuit, including a first impedance matcher, a first bandpass filter, a first wave trap, and a first matching unit. An impedance of the first impedance matcher is a first preset impedance at a first frequency, the first bandpass filter is bridged between a front end of the first impedance matcher and ground, the first bandpass filter enables a signal of the first frequency to pass through, and suppresses at least one of a signal of a second frequency and a signal of third harmonic generation of the first frequency. The second frequency is lower than the first frequency. The first wave trap is bridged between a rear end of the first impedance matcher and the ground.

Abstract: An amplifier circuit, which has a first output terminal and a second output terminal, includes a first charge-steering amplifier, a second charge-steering amplifier, a first switch, and a second switch. The first charge-steering amplifier includes a first input terminal, a second input terminal, a first capacitor, and a second capacitor, and is used for amplifying a first input signal in a first operation period. The second charge-steering amplifier includes a third input terminal, a fourth input terminal, the first capacitor, and the second capacitor, and is used for amplifying a second input signal in a second operation period. The first capacitor and the second capacitor charge during the first operation period and discharge during the second operation period.

Abstract: A semiconductor-on-insulator die can include a power amplifier configured to amplify a radio frequency input signal having a fundamental frequency. The die can further include an output matching circuit including first and second second-order harmonic rejection circuits configured to resonate at about two times the fundamental frequency and a third order harmonic rejection circuit configured to resonate at about three times the fundamental frequency.

Abstract: Methods and apparatus for processing a substrate are provided herein. For example, a matching network configured for use with a plasma processing chamber comprises an input configured to receive one or more radio frequency (RF) signals, an output configured to deliver the one or more RF signals to a processing chamber, a first variable capacitor disposed between the input and the output, a second variable capacitor disposed in parallel to the first variable capacitor, a MEMS array comprising a plurality of variable capacitors connected in series with the first variable capacitor, and a controller configured to tune the matching network between a first frequency for high-power operation and a second frequency for low-power operation.

Abstract: A transistor device includes a transistor cell comprising a channel region, a gate runner that is electrically connected to a gate electrode on the channel region and physically separated from the gate electrode, and a harmonic termination circuit electrically connected to the gate runner between the gate electrode and an input terminal of the transistor device, the harmonic termination circuit configured to terminate signals at a harmonic frequency of a fundamental operating frequency of the transistor device.

Abstract: A matching circuit structure for effectively suppressing the low-frequency clutter of a power amplifier of a mobile phone, falling within the technical field of radio frequency Pas is provided. The circuit structure includes an input end, a blocking capacitor, a power amplifier (PA), an output matching network and an output end connected in series; and the matching circuit structure further includes a negative feedback network connected in parallel to a transmission end of the PA; the negative feedback network includes a resonant capacitor, a resonant inductor and a matching inductor; the resonant capacitor and the resonant inductor are connected in parallel to form a frequency selecting network, and the frequency selecting network is connected in series with the matching inductor and to the ground. The matching circuit structure above can be used to effectively suppress the low-frequency clutter of a power amplifier.

Abstract: Inductance-capacitance (LC) resonators having different resonant frequencies, and radio frequency (RF) transistor amplifiers including the same. One usage of such LC resonators is to implement RF short/DC block circuits. A RF transistor amplifier may include a transistor on a base of the RF transistor amplifier coupled to an input and an output of the RF transistor amplifier; a first inductance-capacitance (LC) resonator comprising a first inductance and a first capacitance; and a second LC resonator comprising a second inductance and a second capacitance. The first LC resonator may be configured to resonate at a first frequency, and the second LC resonator may be configured to resonate at a second frequency different from the first frequency.

Abstract: In one embodiment, the present disclosure is directed to a method for impedance matching. A matching network includes a first reactance element and a second reactance element. A sensor detects a value related to the plasma chamber or the matching network, and a system parameter is determined based on the detected value. For the determined system parameter, an error-related value is calculated for each of a plurality of potential first reactance element positions or for each of a plurality of potential second reactance element positions. A new first reactance element position and a new second reactance element position are calculated based on the error-related values calculated in the prior step. The first reactance element and the second reactance element are then altered to their new positions to reduce a reflected power.

Abstract: Apparatus and methods for power amplifier output matching is disclosed. In one aspect, there is provided an output matching circuit including an input configured to receive an amplified radio frequency signal from a power amplifier, a first output, and a second output. The output matching circuit further includes a first matching circuit electrically connected between the input of the output matching circuit and the first output, the first matching circuit configured to suppress harmonics of a fundamental frequency of the amplified radio frequency signal when the amplified radio frequency signal is within a first band. The output matching circuit further includes a second matching circuit electrically connected between the input of the output matching circuit and the second output, the second matching circuit configured to suppress harmonics of the fundamental frequency of the amplified radio frequency signal when the amplified radio frequency signal is within a second band different from the first band.

Abstract: A radio frequency amplifier includes a transistor, an input impedance matching circuit (e.g., a single-section T-match circuit or a multiple-section bandpass circuit), and a fractional harmonic resonator circuit. The input impedance matching circuit is coupled between an amplification path input and a transistor input terminal. An input of the fractional harmonic resonator circuit is coupled to the amplification path input, and an output of fractional harmonic resonator circuit is coupled to the transistor input terminal. The fractional harmonic resonator circuit is configured to resonate at a resonant frequency that is between a fundamental frequency of operation of the RF amplifier and a second harmonic of the fundamental frequency. According to a further embodiment, the fractional harmonic resonator circuit resonates at a fraction, x, of the fundamental frequency, wherein the fraction is between about 1.25 and about 1.9 (e.g., x?1.5).

Abstract: A first power amplifier amplifies first transmission signals in a first frequency band and outputs the resultant signals. A first matching circuit includes a plurality of first inductor portions and is connected to an output pad electrode of the first power amplifier. A second power amplifier amplifies second transmission signals in a second frequency band higher than the first frequency band and outputs the resultant signals. A second matching circuit includes at least one second inductor portion and is connected to an output side of the second power amplifier. A multilayer substrate has a first main surface and a second main surface located opposite to each other and is provided with the first and second power amplifiers and the first and second matching circuits. The first inductor portion closer than the other first inductor portions to the output pad electrode includes an inner-layer inductor portion located in the multilayer substrate.

Abstract: A power amplifier circuit includes a first amplifier that amplifies a first signal, and a second amplifier arranged subsequent to the first amplifier. The second amplifier amplifies a second signal that is based on an output signal of the first amplifier. The first amplifier performs class inverse-F operation, and the second amplifier performs class F operation.

Abstract: Provided is a probe which transmits an ultrasonic wave to a diagnostic site and receives a reception signal which is a reflected wave.

Abstract: Compact low noise amplifiers that have wide-band coverage while meeting necessary input matching and output matching characteristics. Embodiments include a wide-band, two-stage LNA with minimum degradation in performance compared to multiple narrow-band, single-stage LNAs. A generalized embodiment includes a first amplifier stage having a terminal coupled to a mutually coupled inductor circuit and to a second amplifier stage. The second amplifier stage includes a terminal coupled to the mutually coupled inductor circuit. The mutually coupled inductor circuit comprises electromagnetically coupled inductors L1, L2. Second terminals of the first and second amplifier stages are coupled to respective degeneration inductors. The electromagnetically coupled inductors L1, L2 of the inductor circuit substantially increase the output bandwidth of the LNA with minimum degradation in performance.

Abstract: A multi-mode cone beam computed tomography radiotherapy simulator and treatment machine is disclosed. The radiotherapy simulator and treatment machine both include a rotatable gantry on which is positioned a cone-beam radiation source and a flat panel imager. The flat panel imager captures x-ray image data to generate cone-beam CT volumetric images used to generate a therapy patient position setup and a treatment plan.

Abstract: A power amplifier circuit includes a power amplifier that amplifies an input signal and outputs the amplified signal from an output terminal thereof, a first filter circuit that has a frequency characteristic that attenuates an Nth-order harmonic of the amplified signal, N that is an integer greater than or equal to 2, and a second filter circuit that has a frequency characteristic that attenuates the Nth-order harmonic of the amplified signal. The first filter circuit includes a first capacitor and a first inductor. The first capacitor and the first inductor are connected in series between the output terminal and ground. The second filter circuit includes a second capacitor and a second inductor. The second capacitor and the second inductor are connected in series between the output terminal and ground.

Abstract: One inductor and another inductor are magnetically coupled to each other. A variable current source controls the current flowing in the one inductor. By controlling the current flowing in the one inductor, the inductance value of the other inductor is made variable.

Abstract: A high-frequency power supply circuit includes an amplifier circuit. In the amplifier circuit, one end of an inductor is connected to a direct-current power supply. One end of a switching element is connected to the other end of the inductor. A parallel capacitor is connected in parallel to the switching element. One end of an LC series circuit is connected to the one end of the switching element. A circuit capacitor is connected between the other end of the LC series circuit and the other end of the switching element. The amplifier circuit amplifies a signal having a unique frequency input to a control terminal of the switching element. The amplifier circuit outputs, to a load, a current having the frequency from a connection point between the other end of the LC series circuit and the circuit capacitor.

Abstract: Methods and devices for amplifying an input RF signal according to at least two gain-states is described. According to one aspect, a multi gain amplifier circuit including a low noise amplifier having a stack of transistors is used for amplification of the input RF signal. When switching from a low gain-state to a high gain-state, the drain-to-source voltage of the output transistor of the stack is increased to affect region of operation of the output transistor, and thereby reduce non-linearity at the output of the amplifier. When switching from the high gain-state to the low gain-state, the drain-to-source voltage of the input transistor of the stack is increased to affect region of operation of the input transistor, and thereby reduce non-linearity at the output of the amplifier.

Abstract: A power amplifier circuit includes lower-stage and upper-stage differential amplifying pairs, a combiner, first and second inductors, and first and second capacitors. First and second signals are input into the lower-stage differential amplifying pair. The upper-stage differential amplifying pair outputs first and second amplified signals. The combiner combines the first and second amplified signals. The lower-stage differential amplifying pair includes first and second transistors. A supply voltage is supplied to the collectors of the first and second transistors. The first and second signals are supplied to the bases of the first and second transistors. The upper-stage differential amplifying pair includes third and fourth transistors. A supply voltage is supplied to the collectors of the third and fourth transistors. The emitters of the third and fourth transistors are grounded via the first and second inductors and are connected to the first and second transistors via the first and second capacitors.

Abstract: A radio-frequency module includes a substrate, a first circuit arranged on the substrate and includes a first amplifier for amplifying a diversity signal, and a second circuit arranged on the substrate and includes a second amplifier for amplifying a MIMO signal. The first amplifier and the second amplifier are formed on a single component and are arranged in a central portion in a plan view of the substrate. The first circuit and the second circuit may include a first matching element connected to the first amplifier and a second matching element connected to the second amplifier, respectively. The first amplifier and the second amplifier may be arranged in the central portion on a first main surface of the substrate. The first matching element and the second matching element may be arranged in the central portion on a second main surface of the substrate.

Abstract: The present invention relates to a high-frequency power amplifier in which mainly an amplification GaN chip and a GaAs chip which has a pre-match circuit for the former formed thereon are connected by wires on an identical metal plate. The high-frequency power amplifier according to the present invention is provided with a coupler exhibiting a mutual inductance of a subtractive polarity on the GaAs chip, thereby making it possible to: cancel a mutual inductance between adjacent wires; reduce the spread of a second harmonic impedance with respect to a frequency when a signal source is viewed from a gate terminal of the GaN chip; and maintain a high efficiency of the power amplifier in a desired fundamental wave band.

Abstract: A radio frequency circuit has an amplifier that amplifies an input radio frequency signal, a power supply path that is disposed between an output node of the amplifier and a power supply node to which a DC bias voltage is supplied, and includes a first inductor and a second inductor connected in series, a first resonator that comprises a third inductor and a first capacitor connected in series to the third inductor, and resonates at a series resonance frequency, a second resonator that resonates at a series resonance frequency corresponding to an inductance of the first inductor, a capacitance of the second capacitor, and a resistance value of the first resistor, and a third resonator that comprises a third capacitor connected in parallel with the second inductor, and resonates at a parallel resonance frequency corresponding to a capacitance of the third capacitor and an inductance of the second inductor.

Abstract: Provided is a probe which transmits an ultrasonic wave to a diagnostic site and receives a reception signal which is a reflected wave.

Abstract: A MIM capacitor is included in any one or more of a first matching circuit and a second matching circuit. The mat capacitor performs impedance matching of a fundamental wave included in a high-frequency signal with a transmission line, and forms a short-circuit point for a harmonic included in the high-frequency signal at a connection point with the transmission line.

Abstract: An RF power amplifier includes an amplifier device and a shunt-inductance circuit. The amplifier device includes a substrate, a combining node lead, first and second amplifier dies coupled to the substrate, and first and second output circuits. The first and second amplifier dies are configured to amplify first and second input RF signals, respectively, to produce first and second output RF signals at first and second output terminals, respectively. The first output circuit includes a first inductive path connecting the first output terminal to the lead. The second output circuit includes a second inductive path connecting the second output terminal to the lead. The lead is configured to combine the first and second output RF signals to produce a third output RF signal. The shunt-inductance circuit is coupled between the first output terminal and a ground reference.

Abstract: A ground pad is disposed on a substrate. A plurality of transistors, each grounded at an emitter thereof, are in a first direction on a surface of the substrate. An input line connected to bases of the transistors is on the substrate. At least two shunt inductors are each connected at one end thereof to the input line and connected at the other end thereof to the ground pad. In the first direction, the two shunt inductors are on opposite sides of a center of a region where the transistors are arranged.

Abstract: Various methods and circuital arrangements for protection of an RF amplifier are presented. According to one aspect, the RF amplifier is part of switchable RF paths that may include at least one path with one or more attenuators or switches that can be used during normal operation to define different modes of operation of the at least one path. An RF level detector monitors a level of an RF signal during operation of any one of the switchable RF paths and may control the attenuators or switches to provide an attenuation of the RF signal according to a desired level of protection at an input and/or output of the RF amplifier. According to another aspect, the RF level detector may control a switch to force the RF signal through a different switchable RF path.

Abstract: A multiple-stage amplifier includes a driver stage die and a final stage die. The driver stage die includes a first type of semiconductor substrate (e.g., a silicon substrate), a first transistor, and an integrated portion of an interstage impedance matching circuit. A control terminal of the first transistor is electrically coupled to an RF signal input terminal of the driver stage die, and the integrated portion of the interstage impedance matching circuit is electrically coupled between a current-carrying terminal of the first transistor and an RF signal output terminal of the driver stage die. The second die includes a III-V semiconductor substrate (e.g., a GaN substrate) and a second transistor. A connection, which is a non-integrated portion of the interstage impedance matching circuit, is electrically coupled between the RF signal output terminal of the driver stage die and an RF signal input terminal of the final stage die.

Abstract: An apparatus includes: a transistor including an input terminal for an input signal and an output terminal for an output signal; a matching circuit configured to match a load impedance regarding a fundamental harmonic of at least one of the input signal and the output signal to an impedance of the transistor and include a first conductive film being laminated over the transistor and coupled to at least one of the input terminal and the output terminal; and a processing circuit configured to adjust an impedance regarding a harmonic of at least one of the input signal and the output signal and include a second conductive film being laminated over the first conductive film and coupled to at least one of the input terminal and the output terminal through a via which penetrates through a dielectric layer sandwiched between the first conductive film and the second conductive film.

Abstract: An amplifier may comprise first and second matching networks; first and second transistors; and a transformer including first to third inductors. Also, a gate and a source of the first transistor are connected to the first matching network, one end of the first inductor is connected to a drain of the first transistor, the other end of the first inductor is connected to a source of the second transistor, one end of the second inductor is connected to a gate of the second transistor, the other end of the second inductor is grounded, one end of the third inductor is connected to a drain of the second transistor, and the other end of the third inductor is connected to the second matching network.

Abstract: Systems and methods including variable power amplifier bias impedance are disclosed. In one aspect, there is provided a power amplifier system including a bias circuit configured to receive a bias voltage and generate a bias signal and a power amplifier stage configured to receive an input radio frequency (RF) signal and generate an output RF signal. The power amplifier system may also include a bias impedance component operatively coupled between the bias circuit and the power amplifier stage. The bias impedance is component configured to receive a control signal and adjust an impedance value of the bias impedance component in response to the control signal.

Abstract: A circuit structure for improving the harmonic suppression capability of a radio frequency power amplifier includes an output stage unit, a high-order harmonic suppression unit, and a low-order harmonic suppression unit. The output stage unit outputs a signal to be subjected to harmonic suppression; the high-order harmonic suppression unit comprises a first filter capacitor and a back hole, and is used for suppressing fifth or higher harmonics; the output stage unit and the first filter capacitor are connected to the ground in series by means of the back hole; the low-order harmonic suppression unit is connected to the output stage unit to suppress second, third and fourth harmonics. According to the design, the high-harmonic suppression capability of the radio frequency power amplifier is improved.

Abstract: An amplifier includes a driver stage amplifier transistor and a final stage amplifier transistor, which are integrated in a semiconductor die. The driver stage amplifier transistor has a driver stage input, a driver stage output, and an output impedance, and the driver stage amplifier transistor is configured to operate using a first bias voltage at the driver stage output. The final stage amplifier transistor has a final stage input, a final stage output, and an input impedance. The final stage input is electrically coupled to the driver stage output. The final stage amplifier transistor is configured to operate using a second bias voltage at the final stage output, and the second bias voltage is at least twice as large as the first bias voltage.

Abstract: An interconnect interface is provided to enable communication with an off-package device over a link including a plurality of lanes. Logic of the interconnect interface includes receiver logic to receive a valid signal from the off-package device on a dedicated valid lane of the link indicating that data is to arrive on a plurality of dedicated data lanes in the plurality of lanes, receive the data on the data lanes from the off-package device sampled based on arrival of the valid signal, and receive a stream signal from the off-package device on a dedicated stream lane in the plurality of lanes. The stream signal corresponds to the data and indicates a particular data type of the data. The particular data type can be one of a plurality of different data types capable of being received on the plurality of data lanes of the link.

Abstract: A reconfigurable triplexer that can support more frequency bands than a traditional triplexer is disclosed. For example, the reconfigurable triplexer can handle frequencies of several hundred megahertz up to 10 gigahertz. Further, certain implementations of the reconfigurable multiplexer can reduce or eliminate frequency dead zones that exist with traditional multiplexers. The reconfigurable triplexer includes a multi-stage filter bank capable of supporting a number of frequency bands and a bypass circuit that enables the triplexer to support a variety of sets of frequencies. For instance, unlike traditional triplexers, the reconfigurable triplexer can support both frequency bands with relatively narrow spacing and frequency bands with relatively wide spacing. Further, the inclusion of the bypass circuit enables the reduction or elimination of dead zones between supported frequencies.

Abstract: A wireless multi-band device comprises a radiating system comprising a ground plane layer, a boosting element, and a radiofrequency system, wherein the radiofrequency system comprises a tunable reactive element.

Abstract: The embodiments described herein include amplifiers that are typically used in radio frequency (RF) applications. Specifically, the amplifiers described herein include one or more transient termination circuits coupled to transistor inputs. For example, the transient termination circuits can be configured to reduce the transient response for some signal energy at frequencies below a baseband frequency (fB) of signals being amplified while not similarly reducing the transient response for signal energy near a fundamental frequency (f0) of the signals being amplified.

Abstract: The disclosed technology can include a power amplifier comprising an input, an output, and a transformer. The power amplifier can include a primary inductor coil coupled to the input, a secondary inductor coil coupled to the output, and three harmonic branches coupled to the primary coil. Each branch can comprise at least one electrical component having a tunable impedance.

Abstract: A radio frequency signal amplification device includes an amplification circuit, an impedance matching circuit, a frequency detection circuit, and a control circuit. The amplification circuit has an input terminal and an output terminal. The amplification circuit amplifies a radio frequency (RF) signal received from the input terminal, and generates an amplified radio frequency signal to the output terminal. The impedance matching circuit is coupled to the input terminal or the output terminal of the amplification circuit. The impedance matching circuit receives the radio frequency signal and provides an impedance matching the radio frequency signal, or receives the amplified radio frequency signal and provides an impedance matching the amplified radio frequency signal. The frequency detection circuit determines a frequency band to which the radio frequency signal belongs. The control circuit adjusts the impedance of the impedance matching circuit according to the frequency band.

Abstract: In a radio frequency power amplifier, a semiconductor chip includes at least one first transistor amplifying a radio frequency signal, a first external-connection conductive member connected to the first transistor, a bias circuit including a second transistor that applies a bias voltage to the first transistor, and a second external-connection conductive member connected to the second transistor. The second external-connection conductive member at least partially overlaps with the second transistor when viewed in plan.

Abstract: A multi-gain mode power amplifier, a chip, and a communication terminal. The multi-gain mode power amplifier comprises at least one amplifier circuit. The amplifier circuit comprises a bias circuit, a feedback circuit, a transistor (101), and an input matching network/output matching network. A bias voltage or a control voltage (120) is adjusted to make the feedback circuit to be either turned on or turned off, thus allowing the amplifier circuit to work in a high-gain mode or a low-gain mode. The multi-gain mode power amplifier has different gain modes, fully satisfies the actual demand of the communication terminal to work in the high-gain mode when transmitting a high power and to work in the low-gain mode when transmitting a low power.

Abstract: A transistor device includes a transistor cell comprising a channel region, a gate runner that is electrically connected to a gate electrode on the channel region and physically separated from the gate electrode, and a harmonic termination circuit electrically connected to the gate runner between the gate electrode and an input terminal of the transistor device, the harmonic termination circuit configured to terminate signals at a harmonic frequency of a fundamental operating frequency of the transistor device.

Abstract: A semiconductor device includes a semiconductor substrate, a transistor, and a first harmonic termination circuit. The transistor is formed at the semiconductor substrate. The transistor amplifies an input signal supplied to an input end and outputs an amplified signal through an output end. The first harmonic termination circuit attenuates a harmonic component included in the amplified signal. The first harmonic termination circuit is formed at the semiconductor substrate such that one end of the first harmonic termination circuit is connected to the output end of the transistor and the other end of the first harmonic termination circuit is connected to a ground end of the transistor.

Abstract: Radio frequency (RF) amplifier circuitry includes an input node, an output node, an amplifier, and bootstrap circuitry. The amplifier includes a control node coupled to the input node, a first amplifier node coupled to the output node, and a second amplifier node coupled to a fixed potential. The amplifier is configured to receive an input signal having a first frequency at the control node and change an impedance between the first amplifier node and the second amplifier node based on the input signal. The bootstrap circuitry is coupled between the control node and the second amplifier node. The bootstrap circuitry is configured to provide a low impedance path between the control node and the second amplifier node for signals having a second frequency that is equal to about twice the first frequency and provide a high impedance path for signals having a frequency outside the second frequency.

Abstract: A power amplifier is provided having an input for receiving a signal to be amplified that is associated with a fundamental frequency. An amplifier circuit of the power amplifier includes an active device for amplifying the input signal and an output for providing the amplified signal to a load. A load network is electrically interposed between the amplifier circuit and the output and includes fundamental frequency matching circuitry which presents an optimal resistance at the fundamental frequency. The load network further includes a parallel transmission line arrangement having, at the fundamental frequency, a one-eighth wavelength short-circuited stub and a one-eighth wavelength open-circuit stub. The fundamental frequency matching circuitry and the parallel transmission line arrangement cooperate such that the load network operatively presents an optimal resistance at the fundamental frequency, an open-circuit at a second harmonic frequency and a short-circuit at a third harmonic frequency.

Abstract: A power amplifier circuit includes an amplifier that receives an input signal with an alternating current and outputs an output signal obtained by amplifying power of the input signal to a first node; an inductive element that is connected between the first node and a second node; and a variable capacitor that is connected between the second node and a reference potential, and whose electrostatic capacitance increases as power of the output signal increases.