An amplifier is formed in a wiring layer. A semiconductor device includes a second layer over a first layer with a metal oxide therebetween. The first layer includes a first transistor including a first semiconductor layer containing silicon. The second layer includes an impedance matching circuit, and the impedance matching circuit includes a second transistor including a second semiconductor layer containing gallium. The first transistor forms first coupling capacitance between the first transistor and the metal oxide, and the impedance matching circuit forms second coupling capacitance between the impedance matching circuit and the metal oxide. The impedance matching circuit is electrically connected to the metal oxide through the second coupling capacitance. The metal oxide inhibits the influence of first radiation noise emitted from the impedance matching circuit on the operation of the first transistor.

A radio-frequency module includes a module substrate, a power amplifier, and a control circuit configured to control the power amplifier. The control circuit includes a temperature sensor. The power amplifier and the control circuit are stacked one on top of another on a principal surface of the module substrate.

Methods and apparatus are provided. In an example aspect, an amplifier protection circuit is provided. The amplifier protection circuit comprises an input for receiving a signal from a first amplifier, and an isolation circuit between the input and an output of the amplifier protection circuit. The isolation circuit is configured to sense a backward signal propagating from the output of the amplifier protection circuit towards the input to provide a sensed signal, and to provide at least one cancellation signal based on the sensed signal to at least partially cancel the backward signal.

A radio-frequency circuit is provided that includes a power amplifier, a control circuit, an on-off switch, a connection terminal, and a mount board. The power amplifier supports an APT system and an ET system. The control circuit controls the power amplifier by using the APT system and the ET system. The on-off switch is connected in series to a capacitive element connected between a path and the ground. The connection terminal is connected to the capacitive element. Moreover, the control circuit overlies the connection terminal in plan view in the thickness direction of the mount board.

A switched capacitor modulator (SCM) includes a RF power amplifier. The RF power amplifier receives a rectified voltage and a RF drive signal and modulates an input signal in accordance with the rectified voltage to generate a RF output signal to an output terminal. A reactance in parallel with the output terminal is configured to vary in response to a control signal to vary an equivalent reactance in parallel with the output terminal. A controller generates the control signal and a commanded phase. The commanded phase controls the RF drive signal. The reactance is at least one of a capacitance or an inductance, and the capacitance or the inductance varies in accordance with the control signal.

A switched capacitor modulator (SCM) includes a RF power amplifier. The RF power amplifier receives a rectified voltage and a RF drive signal and modulates an input signal in accordance with the rectified voltage to generate a RF output signal to an output terminal. A reactance in parallel with the output terminal is configured to vary in response to a control signal to vary an equivalent reactance in parallel with the output terminal. A controller generates the control signal and a commanded phase. The commanded phase controls the RF drive signal. The reactance is at least one of a capacitance or an inductance, and the capacitance or the inductance varies in accordance with the control signal.

In a power amplifying module in which a plurality of differential amplifying circuits is mounted on a substrate, each of the differential amplifying circuits includes a chip device that includes at least two amplifiers, each of the at least two amplifiers amplifying a differential signal, a balun that includes a primary side winding wire and a secondary side winding wire, both ends of the primary side winding wire being connected to an output of the chip device, and a capacitor provided between a power feed point of the primary side winding wire and a reference potential. In at least one of the plurality of the differential amplifying circuits, the distance from one end of the primary side winding wire to the power feed point is different from the distance from the other end of the primary side winding wire to the power feed point.

A first primary line has a first node at one end and a third node at another end and transmits a radio-frequency signal between the first node and the third node. A second primary line has a second node at one end and a fourth node at another end and transmits a radio-frequency signal between the second node and the fourth node. A first secondary line has a portion connected to the second node and is electromagnetically coupled to the first primary line. The second secondary line has a portion connected to the first node and has another end connected to a portion of the first secondary line. The second secondary line is electromagnetically coupled to the second primary line. A first capacitor is connected in parallel to a portion of the second primary line or a portion of the second secondary line.

A semiconductor device is provided in which power consumption is reduced and an increase in circuit area is inhibited. The semiconductor device includes a high frequency amplifier circuit, an envelope detection circuit, and a power supply circuit. The power supply circuit has a function of supplying a power supply potential to the high frequency amplifier circuit, an output of the high frequency amplifier circuit is connected to the envelope detection circuit, and an output of the envelope detection circuit is connected to the power supply circuit. The power supply circuit can reduce the power consumption by changing the power supply potential in accordance with the output of the high frequency amplifier circuit. The use of an OS transistor in the envelope detection circuit can inhibit an increase in circuit area.

A semiconductor device is provided in which power consumption is reduced and an increase in circuit area is inhibited. The semiconductor device includes a high frequency amplifier circuit, an envelope detection circuit, and a power supply circuit. The power supply circuit has a function of supplying a power supply potential to the high frequency amplifier circuit, an output of the high frequency amplifier circuit is connected to the envelope detection circuit, and an output of the envelope detection circuit is connected to the power supply circuit. The power supply circuit can reduce the power consumption by changing the power supply potential in accordance with the output of the high frequency amplifier circuit. The use of an OS transistor in the envelope detection circuit can inhibit an increase in circuit area.