Bias circuit

A bias circuit that supplies a first bias current or voltage to an amplifier that amplifies a radio frequency signal, the bias circuit comprising:

• a field-effect transistor (FET), wherein a power supply voltage is supplied to a drain of the FET and a source of the FET outputs the first bias current or voltage;
• a first bipolar transistor, wherein a collector of the first bipolar transistor is connected to a gate of the FET, a base of the first bipolar transistor is connected to the source of the FET, the first bipolar transistor has a common emitter, and a constant current is supplied to the collector of the first bipolar transistor;
• and
• a first capacitor, wherein a first end of the first capacitor is connected to the collector of the first bipolar transistor and the first capacitor suppresses variations in a collector voltage of the first bipolar transistor.