Supply modulator for polar power amplifier

A method comprising:

• providing a phase modulated (PM) signal to an amplifier;
• providing, from a modulator, a supply voltage to the amplifier;
• varying the supply voltage based on an amplitude modulated (AM) signal provided to the modulator;
• increasing a bias current provided from a current source to the modulator responsive to detecting, using a detector circuit, the supply voltage exceeding a first threshold;
• and
• increasing the bias current provided to the modulator responsive to the detector circuit detecting the supply voltage falling below a second threshold, the second threshold being less than the first threshold.

A system comprising:

• a baseband circuit configured to output an amplitude modulated (AM) and a phase modulated (PM) signal;
• a amplifier coupled to receive the PM signal;
• a modulator coupled to receive the AM signal and coupled to provide a supply voltage to the amplifier and further configured to vary the supply voltage based on the AM signal;
• and
• a detector circuit configured to cause an increase to a bias current provided to circuitry in the modulator responsive to detecting the supply voltage exceeding a first threshold, and further configured to cause an increase to the bias current responsive to detecting the supply voltage falling below a second threshold, the second threshold being less than the first threshold.