An amplifier unit includes an amplifier, a bias circuit, an inductor, a variable resistor circuit, and a control circuit. The amplifier includes an amplifier transistor that amplifies an input radio-frequency signal. The bias circuit is connected to the amplifier. The inductor is connected between and in series with the amplifier and the bias circuit. The variable resistor circuit is connected to the inductor. The control circuit includes a measuring circuit and a comparison circuit. The measuring circuit measures an amplification characteristic value of the amplifier transistor. The comparison circuit compares the amplification characteristic value measured by the measuring circuit with a reference value. The control circuit controls the variable resistor circuit based on a comparison result of the comparison circuit.

To achieve miniaturization. A matching circuit is connected to a connection terminal that is one of an input terminal and an output terminal of an amplifier. A mounting substrate has a ground layer. The matching circuit includes a main line, a sub-line, and an IC chip. The main line is formed of a first conductor pattern intersecting a thickness direction of the mounting substrate, and is connected to a connection terminal of the amplifier. The sub-line is formed of a second conductor pattern intersecting the thickness direction of the mounting substrate, and is connected between the main line and the ground layer. The sub-line is opposed to the main line in the thickness direction of the mounting substrate. The IC chip is disposed on the mounting substrate, and includes an adjustment unit that adjusts impedance conversion characteristics of the matching circuit.

To achieve miniaturization. A matching circuit is connected to a connection terminal that is one of an input terminal and an output terminal of an amplifier. A mounting substrate has a ground layer. The matching circuit includes a main line, a sub-line, and an IC chip. The main line is formed of a first conductor pattern intersecting a thickness direction of the mounting substrate, and is connected to a connection terminal of the amplifier. The sub-line is formed of a second conductor pattern intersecting the thickness direction of the mounting substrate, and is connected between the main line and the ground layer. The sub-line is opposed to the main line in the thickness direction of the mounting substrate. The IC chip is disposed on the mounting substrate, and includes an adjustment unit that adjusts impedance conversion characteristics of the matching circuit.

The disclosure relates to a pre-5.sup.th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4.sup.th-Generation (4G) communication system, such as long term evolution (LTE). A transformer is provided. The transformer includes a first primary inductor, a second primary inductor, and a secondary inductor. The secondary inductor may be disposed between the first primary inductor and the second primary inductor. The secondary inductor may be disposed spaced apart from the first primary inductor and the second primary inductor.

The disclosure relates to a pre-5.sup.th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4.sup.th-Generation (4G) communication system, such as long term evolution (LTE). A transformer is provided. The transformer includes a first primary inductor, a second primary inductor, and a secondary inductor. The secondary inductor may be disposed between the first primary inductor and the second primary inductor. The secondary inductor may be disposed spaced apart from the first primary inductor and the second primary inductor.

A power amplifier circuit includes a power amplifier, first and second filters, and first and second output paths. The power amplifier is able to amplify both of a first signal and a second signal. The frequency of the second signal is higher than that of the first signal. The first filter includes a first inductor and attenuates the second signal amplified in the power amplifier. The first inductor serves as a path for the first signal amplified in the power amplifier. The second filter includes a first capacitor and attenuates the first signal amplified in the power amplifier. The first capacitor serves as a path for the second signal amplified in the power amplifier. The first signal outputted from the first filter is supplied to the first output path. The second signal outputted from the second filter is supplied to the second output path.

A power amplifier circuit includes a power amplifier, first and second filters, and first and second output paths. The power amplifier is able to amplify both of a first signal and a second signal. The frequency of the second signal is higher than that of the first signal. The first filter includes a first inductor and attenuates the second signal amplified in the power amplifier. The first inductor serves as a path for the first signal amplified in the power amplifier. The second filter includes a first capacitor and attenuates the first signal amplified in the power amplifier. The first capacitor serves as a path for the second signal amplified in the power amplifier. The first signal outputted from the first filter is supplied to the first output path. The second signal outputted from the second filter is supplied to the second output path.

Methods and apparatus for limiting the input voltage (swing) of a power amplifier, such as a power amplifier in a radio frequency (RF) front-end of a wireless device. One example radio frequency front-end circuit generally includes a power amplifier, a matching circuit having an output coupled to an input of the power amplifier, and an overvoltage protection circuit coupled to the matching circuit. With an overvoltage protection circuit coupled to the matching circuit in this manner, the power amplifier may have enhanced ruggedness performance.

Methods and apparatus for limiting the input voltage (swing) of a power amplifier, such as a power amplifier in a radio frequency (RF) front-end of a wireless device. One example radio frequency front-end circuit generally includes a power amplifier, a matching circuit having an output coupled to an input of the power amplifier, and an overvoltage protection circuit coupled to the matching circuit. With an overvoltage protection circuit coupled to the matching circuit in this manner, the power amplifier may have enhanced ruggedness performance.

A radio frequency switch circuit includes a negative voltage generating circuit, a notch network, a logic control circuit, and a radio frequency switching circuit. The logic control circuit can be configured to, upon being driven by the negative voltage signal generated by the negative voltage generating circuit, control the operating modes of the radio frequency switching circuit; and the notch network is connected between the negative voltage generating circuit and the logic control circuit. As such, the influence of radio frequency signals generated by the radio frequency switching circuit can be filtered through the notch network, and the interference of radio frequency signals to the negative voltage generating circuit can be reduced, thereby improving the performance of the radio frequency switch circuit, for example in insertion loss, isolation and harmonic suppression.