Power amplifier circuit

A power amplifier circuit comprising:

• an amplifier transistor having a base or a gate to which an input signal is supplied, and having a collector or a drain from which an amplified signal is output, the amplified signal being obtained by amplifying the input signal;
• a bias circuit configured to supply a bias current or a bias voltage to the base or the gate of the amplifier transistor;
• and
• a resistance element connected in series between the base of the amplifier transistor and the bias circuit, or between the gate of the amplifier transistor and the bias circuit, wherein:
• the bias circuit comprises:
• a voltage generation circuit configured to generate a first direct-current voltage in accordance with a control signal;
• a first transistor having a base or a gate to which the first direct-current voltage is supplied, and having an emitter or a source from which the bias current or the bias voltage is supplied to the base or the gate of the amplifier transistor via the resistance element;
• a second transistor having a base or a gate to which a second direct-current voltage is supplied, and having an emitter or a source connected to the emitter or the source of the first transistor;
• a signal supply circuit disposed between the base or the gate of the second transistor and a supply path of the input signal to the amplifier transistor, the signal supply circuit being configured to supply the input signal to the base or the gate of the second transistor;
• and
• an impedance circuit disposed between the base or the gate of the first transistor and the base or the gate of the second transistor,
• when the power amplifier circuit operates in a first mode, the voltage generation circuit is configured to be kept in an on state by the control signal, and
• when the power amplifier circuit operates in a second mode, the voltage generation circuit is configured to be kept in an off state by the control signal, the second mode being a mode in which a power level of the amplified signal is less than a power level of the amplified signal in the first mode.