Radio-frequency signal amplifier circuit, power amplifier module, front-end circuit, and communication device

A radio-frequency signal amplifier circuit of a front-end circuit configured to propagate a radio-frequency transmission signal and a radio-frequency reception signal, comprising:

• an amplifier transistor configured to amplify the radio-frequency transmission signal;
• a bias circuit configured to supply a bias signal to an input terminal of the amplifier transistor;
• a first resistance element having a first end connected to the bias circuit and a second end connected to the input terminal of the amplifier transistor;
• and
• an LC series resonance circuit having a first end connected to a node between the first resistance element and the input terminal and a second end connected to a ground terminal, the LC series resonant circuit comprising an inductor and a capacitor that are connected in series to each other,
• wherein a resonant frequency of the LC series resonance circuit is in a difference frequency band representing a difference between a frequency band of the radio-frequency transmission signal and a frequency band of the radio-frequency reception signal.