US 12,407,309 B2
Radio-frequency circuit and communication device
Masakazu Hirobe, Kyoto (JP)
Assigned to MURATA MANUFACTURING CO., LTD., Kyoto (JP)
Filed by Murata Manufacturing Co., Ltd., Kyoto (JP)
Filed on Nov. 15, 2022, as Appl. No. 18/055,439.
Application 18/055,439 is a continuation of application No. PCT/JP2021/002727, filed on Jan. 27, 2021.
Claims priority of application No. 2020-106480 (JP), filed on Jun. 19, 2020.
Prior Publication US 2023/0077189 A1, Mar. 9, 2023
Int. Cl. H03F 1/30 (2006.01); H03F 3/24 (2006.01)
CPC H03F 3/245 (2013.01) [H03F 2200/451 (2013.01); H03F 2200/78 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A radio-frequency circuit comprising:
an amplifier circuit comprising a specific transistor that has an input terminal and an output terminal, and that is configured to amplify a radio-frequency signal input to the input terminal and to output an amplified radio-frequency signal from the output terminal;
a bias circuit configured to supply a bias current or a bias voltage to the input terminal of the specific transistor;
a bias control circuit configured to supply a control current or a control voltage to the bias circuit;
comparing circuitry configured to compare a threshold voltage with a power supply voltage of a power supply terminal, the power supply terminal being connected to the output terminal of the specific transistor;
a variable resistance circuit connected between the power supply terminal and the output terminal, and comprising a first resistive circuit element and a first switch connected in parallel with each other; and
control circuitry configured to change a resistance value of the variable resistance circuit in accordance with a result of the comparing circuitry.