Power amplifier circuit

A power amplifier circuit comprising:

• a first amplifier transistor comprising a base or gate configured to receive a first signal inputted, the first signal comprising one balanced signal, a collector or drain configured to output a first amplified signal generated by amplifying the first signal, and an emitter or source that is electrically connected to ground;
• a second amplifier transistor comprising a base or gate configured to receive a second signal inputted, the second signal comprising a second balanced signal, a collector or drain configured to output a second amplified signal generated by amplifying the second signal, and an emitter or source that is electrically connected to the ground;
• a first variable capacitance electrically coupled between the collector or drain of the second amplifier transistor and the base or gate of the first amplifier transistor;
• and
• a second variable capacitance electrically coupled between the collector or drain of the first amplifier transistor and the base or gate of the second amplifier transistor,
• wherein the first variable capacitance comprises a first capacitor and a first switch that are coupled in series with each other, and
• wherein the second variable capacitance comprises a second capacitor and a second switch that are coupled in series with each other.