Envelope tracking current bias circuit and power amplifier apparatus

A power amplifier apparatus comprising:

• an envelope tracking current bias circuit configured to generate a first envelope tracking bias current based on an envelope voltage of an input signal;
• and
• a power amplifier circuit configured to be current biased based on the first envelope tracking bias current to amplify power of the input signal;
• wherein the power amplifier circuit comprises:
• a power amplifier configured to receive the input signal at a base of the power amplifier and amplify the power of the input signal;
• and
• a buffered bias circuit configured to generate a second envelope tracking bias current based on the first envelope tracking bias current, and supply the second envelope tracking bias current to the base of the power amplifier to reduce AM-PM distortion of the power amplifier circuit.

A power amplifier apparatus comprising:

• a power amplifier having a base and configured amplify an input signal applied to the base;
• a tracking current bias circuit configured to generate a first tracking bias current based on a fixed reference value and a time-varying parameter of the input signal;
• and
• a buffered bias circuit configured to amplify the first tracking bias current to generate a second tracking bias current, and apply the second tracking bias current to the base of the power amplifier to reduce amplitude modulation-phase modulation (AM-PM) distortion of the power amplifier.