Power amplifier circuit

A power amplifier circuit comprising:

• a first amplifier configured to amplify a first radio frequency (RF) signal supplied to the first amplifier, and to output a second RF signal;
• a second amplifier configured to amplify the second RF signal supplied to the second amplifier, and to output a third RF signal;
• a bias circuit configured to supply a bias current or a bias voltage to the first amplifier or to the second amplifier;
• and
• a bias adjustment circuit configured to adjust the bias current or the bias voltage based on the first RF signal, the second RF signal, or the third RF signal,
• wherein the bias adjustment circuit comprises a first diode having an anode to which a control signal is input, and a cathode connected to ground, the control signal being indicative of the first RF signal, the second RF signal, or the third RF signal,
• wherein the bias circuit comprises a bias transistor configured to output the bias current or the bias voltage based on a voltage at the anode of the first diode,
• wherein the first amplifier has a first supply terminal to which the first RF signal is supplied, and a first output terminal from which the second RF signal is output,
• wherein the second amplifier has a second supply terminal connected to the first output terminal of the first amplifier and to which the second RF signal is supplied, and a second output terminal from which the third RF signal is output,
• wherein the bias transistor has an emitter connected to the first supply terminal or to the second supply terminal,
• wherein the anode of the first diode is connected to the first supply terminal, the first output terminal, or the second output terminal, and
• wherein the bias transistor further has a base connected to the anode of the first diode.