Abstract: A power amplifier circuit includes: a first switch circuit that switches conduction and non-conduction between a node between the drive stage amplifier and the power stage amplifier and an output terminal, and a second switch circuit that switches conduction and non-conduction between the power stage amplifier and the output terminal. The power amplifier circuit has a first mode in which the first switch circuit is made conductive and the second switch circuit is made non-conductive, and a second mode in which the first switch circuit is made non-conductive and the second switch circuit is made conductive. The power amplifier circuit makes, when shifting from the first mode to the second mode, the first switch circuit non-conductive after making the second switch circuit conductive, and makes, when shifting from the second mode to the first mode, the second switch circuit non-conductive after making the first switch circuit conductive.

Abstract: An amplifier circuit includes: a second FET connected, together with a first FET, between a power supply and a reference potential; a first voltage divider resistor circuit; a first switch element; a second voltage divider resistor circuit; a third voltage divider resistor circuit; and a second switch element. The first FET and the second FET have their adjacent drains and sources connected. Each resistance value of the second voltage divider resistor circuit is greater than each resistance value of the first voltage divider resistor circuit. Each resistance value of the third voltage divider resistor circuit is less than each resistance value of the second voltage divider resistor circuit. The second voltage divider resistor circuit and the third voltage divider resistor circuit have an identical voltage division ratio.

Abstract: An amplifier circuit includes: an input terminal; a first FET having a gate; a second FET connected, together with the first FET, between a power supply and a reference potential; an output terminal provided between the second FET and a load to output an amplified signal; a first voltage divider resistor circuit that divides a potential difference between the power supply and the reference potential, and generates a bias to be applied to a gate of the second FET; and a first switch element provided between the first voltage divider resistor circuit and the power supply and for turning on/off an electrical connection between the power supply and the first voltage divider resistor circuit. The first FET and the second FET have their adjacent drains and sources connected. The first switch element turns off when amplification operation by the first FET and the second FET is not performed.

Abstract: An amplification circuit includes an input terminal to which a signal to be amplified is input, a first FET having a gate to which a signal input to the input terminal is applied, second and third FETs that are connected between a power supply and a reference potential, an output terminal that is provided between a load and the third FET nearest to the power supply and configured to output an amplified signal, a voltage-dividing resistor circuit configured to generate a bias to be applied to gates of the second and third FETs, and a clamping circuit configured to clamp a bias to be applied to the gate of the third FET when a bias to be applied from the voltage-dividing resistor circuit to the gate of the second FET exceeds a predetermined reference voltage. The first to third FETS are vertically stacked and connected.

Abstract: An amplifier device includes an amplifier including cascade-connected power amplifiers in a plurality of stages and a bias circuit configured to supply bias currents to the amplifier. A bias current supplied to a power amplifier in the first stage of the power amplifiers in the plurality of stages exhibits a positive temperature characteristic. A bias current supplied to a power amplifier in the final stage exhibits a negative temperature characteristic.

Abstract: A switching circuit includes: a substrate including input-and-output terminals; a switch provided to the substrate and including a source terminal, a gate terminal, and a drain terminal, the source terminal being connected to an input end of a power amplifier, the drain terminal being connected to a first input-and-output terminal; a voltage control circuit provided to the substrate and connected to the gate terminal; a switch provided to the substrate and including a source terminal, a gate terminal, and a drain terminal, the source terminal being connected to a second input-and-output terminal, the drain terminal being connected to an output end of the power amplifier; and a voltage control circuit provided to the substrate to be apart from the voltage control circuit and connected to the gate terminal.

Abstract: An amplifier circuit includes an input terminal, an output terminal, a transistor provided in between the input terminal and the output terminal, and a coiled or meandered inductor. The transistor has a gate, a source, and a drain, and of these gate, source, and drain, two terminals are connected to ground terminals that are different from each other. The inductor is connected between the ground terminals to which the foregoing two terminals are connected.

Abstract: An amplifier circuit includes: a transistor provided between an input terminal and an output terminal and having a gate connected to the input terminal, a source connected to a ground, and a drain connected to the output terminal; an inductor connected between the source and the ground; an inductor connected between the gate and the input terminal, and switches connected to at least one of the inductors and configured to change a mutual inductance of the inductors.

Abstract: An amplifier circuit amplifies a radio-frequency signal. The amplifier circuit includes an amplifier, an input matching circuit connected to an input side of the amplifier and matches impedance, and a protection circuit connected to a node in a path within a path between an input matching circuit and the amplifier. The protection circuit includes a first diode connected between the node and a ground, and a second diode connected in parallel with the first diode and connected in a direction opposite to the first diode between the node and the ground. A threshold voltage of each of the first diode and the second diode is greater than a maximum voltage amplitude of the input signal at the node and is less than a difference between a withstand voltage of the amplifier and the bias voltage.

Abstract: An amplifying apparatus includes a transistor arranged on a substrate and constituting an amplifier, an input terminal for inputting a high-frequency signal to the amplifier, an output terminal for outputting the high-frequency signal amplified by the amplifier, a first inductor formed in or on the substrate and connected between a source of the transistor and a ground, and a second inductor formed in or on the substrate and connected between a gate of the transistor and the input terminal. When the substrate is viewed in a plan view, the first inductor and the second inductor do not overlap each other. The first inductor and the second inductor are magnetically coupled to each other.

Abstract: An amplifier device includes an amplifier including cascade-connected power amplifiers in a plurality of stages and a bias circuit configured to supply bias currents to the amplifier. A bias current supplied to a power amplifier in the first stage of the power amplifiers in the plurality of stages exhibits a positive temperature characteristic. A bias current supplied to a power amplifier in the final stage exhibits a negative temperature characteristic.

Abstract: An amplifier circuit includes: a transistor provided between an input terminal and an output terminal and having a gate connected to the input terminal, a source connected to a ground, and a drain connected to the output terminal; an inductor connected between the source and the ground; an inductor connected between the gate and the input terminal, and switches connected to at least one of the inductors and configured to change a mutual inductance of the inductors.

Abstract: An amplifier circuit amplifies a radio-frequency signal. The amplifier circuit includes an amplifier, an input matching circuit connected to an input side of the amplifier and matches impedance, and a protection circuit connected to a node in a path within a path between an input matching circuit and the amplifier. The protection circuit includes a first diode connected between the node and a ground, and a second diode connected in parallel with the first diode and connected in a direction opposite to the first diode between the node and the ground. A threshold voltage of each of the first diode and the second diode is greater than a maximum voltage amplitude of the input signal at the node and is less than a difference between a withstand voltage of the amplifier and the bias voltage.

Abstract: A voltage supply circuit includes a level shifter that switches between voltages of two voltage input units and that outputs one of the voltages, a charge pump that transforms a voltage of an input power supply and that applies the transformed voltage to the level shifter, and a charge pump control circuit. The voltage supply circuit controls supply and interruption of a predetermined voltage to a voltage-supplied circuit (RF switch 20). The charge pump control circuit causes the charge pump to perform a continuous operation in an on-mode and to perform an intermittent operation in an off-mode, the off-mode representing a state in which the voltage supply to the voltage-supplied circuit (RF switch 20) is stopped, the on-mode representing a state in which the predetermined voltage is supplied.

Abstract: An amplifying apparatus includes a transistor arranged on a substrate and constituting an amplifier, an input terminal for inputting a high-frequency signal to the amplifier, an output terminal for outputting the high-frequency signal amplified by the amplifier, a first inductor formed in or on the substrate and connected between a source of the transistor and a ground, and a second inductor formed in or on the substrate and connected between a gate of the transistor and the input terminal. When the substrate is viewed in a plan view, the first inductor and the second inductor do not overlap each other. The first inductor and the second inductor are magnetically coupled to each other.

Abstract: A voltage supply circuit includes a level shifter that switches between voltages of two voltage input units and that outputs one of the voltages, a charge pump that transforms a voltage of an input power supply and that applies the transformed voltage to the level shifter, and a charge pump control circuit. The voltage supply circuit controls supply and interruption of a predetermined voltage to a voltage-supplied circuit (RF switch 20). The charge pump control circuit causes the charge pump to perform a continuous operation in an on-mode and to perform an intermittent operation in an off-mode, the off-mode representing a state in which the voltage supply to the voltage-supplied circuit (RF switch 20) is stopped, the on-mode representing a state in which the predetermined voltage is supplied.

Abstract: Provided is an amplification circuit that amplifies an input signal and outputs an amplified signal. The amplification circuit includes: an amplification element that outputs the amplified signal from an output terminal thereof; an inductor having one end to which a power supply voltage is supplied and another end that is connected to the output terminal of the amplification element; a variable resistor that is connected in parallel with the inductor; and a resistance value adjusting circuit that adjusts a resistance value of the variable resistor in accordance with the temperature.

Abstract: Provided is an amplification circuit that amplifies an input signal and outputs an amplified signal. The amplification circuit includes: an amplification element that outputs the amplified signal from an output terminal thereof; an inductor having one end to which a power supply voltage is supplied and another end that is connected to the output terminal of the amplification element; a variable resistor that is connected in parallel with the inductor; and a resistance value adjusting circuit that adjusts a resistance value of the variable resistor in accordance with the temperature.

Abstract: Provided is an amplification circuit that amplifies an input signal and outputs an amplified signal. The amplification circuit includes: an amplification element that outputs the amplified signal from an output terminal thereof; an inductor having one end to which a power supply voltage is supplied and another end that is connected to the output terminal of the amplification element; a variable resistor that is connected in parallel with the inductor; and a resistance value adjusting circuit that adjusts a resistance value of the variable resistor in accordance with the temperature.

Abstract: Provided is an amplification circuit that amplifies an input signal and outputs an amplified signal. The amplification circuit includes: an amplification element that outputs the amplified signal from an output terminal thereof; an inductor having one end to which a power supply voltage is supplied and another end that is connected to the output terminal of the amplification element; a variable resistor that is connected in parallel with the inductor; and a resistance value adjusting circuit that adjusts a resistance value of the variable resistor in accordance with the temperature.