Murata Manufacturing Co., Ltd.

Masakazu Hirobe

Takanori Uejima

Yoshihiro Daimon

Nanami Yumura

A radio-frequency circuit includes an amplifier circuit, a bias circuit, a bias control circuit, a comparing section, a signal input terminal, an antenna terminal, an attenuation circuit, and a control unit. The amplifier circuit includes a specific transistor. The bias circuit supplies a bias current or a bias voltage to the input terminal of the specific transistor. The bias control circuit supplies a control current or a control voltage to the bias circuit. The comparing section compares a threshold voltage with a power supply voltage of a power supply terminal connected to the output terminal of the specific transistor. The attenuation circuit is connected in a signal path between the signal input terminal and the antenna terminal and is capable of attenuating the radio-frequency signal. The control unit changes an attenuation of the attenuation circuit in accordance with a compared result of the comparing section.

Radio-frequency circuit and communication device

A radio-frequency circuit includes an amplifier circuit, a bias circuit, a bias control circuit, a comparing section, a variable resistance circuit, and a control unit. The amplifier circuit includes a transistor that amplifies a radio-frequency signal input to an input terminal and outputs the radio-frequency signal from an output terminal. The bias circuit supplies a bias current or a bias voltage to the input terminal of the transistor. The comparing section compares a threshold voltage with a power supply voltage of a power supply terminal connected to the output terminal of the transistor. The variable resistance circuit is connected between the power supply terminal and the output terminal. The variable resistance circuit includes a parallel circuit made up of a resistive element and a switch element. The control unit changes a resistance value of the variable resistance circuit in accordance with a compared result of the comparing section.

A power amplifier circuit includes an amplifier circuit, a bias circuit, a detector, and a control circuit. The amplifier circuit includes a first bipolar transistor. The bias circuit includes an emitter follower. The emitter follower includes a second bipolar transistor and supplies a bias current to the base of the first bipolar transistor. The detector detects the voltage of a power supply terminal connected to the collector of the first bipolar transistor. The control circuit includes a current limiting circuit disposed between a battery terminal and the collector of the second bipolar transistor. The control circuit changes an upper limit value of a control current to be supplied to the collector of the second bipolar transistor, based on the voltage detected by the detector.

Power amplifier circuit

A radio frequency module includes a transmit filter that allows a transmit signal of a band A for FDD to pass through, a receive filter that allows a receive signal of the band A to pass through, a filter that allows a transmit/receive signal of a band B for TDD to pass through, power amplifiers, a low noise amplifier, a switch between connecting the receive filter to the low noise amplifier and connecting the filter to the low noise amplifier, a switch between connecting the filter to the power amplifier and connecting the filter to the low noise amplifier, a matching circuit connected between the power amplifier and the transmit filter, a matching circuit connected between the power amplifier and the switch, and a module board. On the module board, each of the power amplifiers and the switch is arranged in between the matching circuit and the matching circuit.

Radio frequency module and communication device

A power amplification module includes an amplification circuit, a biasing circuit, a constant voltage generation circuit, a constant current generation circuit, a switching unit, and a control unit for controlling a switching operation of the switching unit, and the control unit causes the switching unit to perform switching to connect the constant voltage generation circuit to an input end of the biasing circuit when an output mode is a first output mode in which a high-frequency signal having no less than a predetermined output power is outputted from the amplification circuit, and causes the switching unit to perform switching to connect the constant current generation circuit to the input end of the biasing circuit when the output mode is a second output mode in which a power less than the predetermined output power is outputted from the amplification circuit.

Power amplification module, method for controlling power amplification module, and high-frequency front end circuit

A high-frequency front end circuit performs reception/transmission simultaneously, and includes a transmitter circuit and a receiver circuit. The transmitter circuit includes a transmit filter passing a signal in the transmit frequency band. The receiver circuit includes a receive filter, an LNA, and a filter circuit. The receive filter passes a signal in the receive frequency band different from the transmit frequency band. The LNA receives and amplifies a signal that has been output from the receive filter. The filter circuit is connected between the receive filter and the LNA. The filter circuit attenuates a component, which is included in the signal received by the LNA, of the frequency indicating the difference between the center frequency of the transmit frequency band and the center frequency of the receive frequency band.

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Kyoto, Japan

Masakazu Hirobe