Source follower based envelope tracking for power amplifier biasing

A power amplifier bias circuit with embedded envelope detection comprising:

• an envelope detector circuit configured to generate a baseband envelope tracking bias signal to bias a power amplifier, the envelope detector circuit including:
• a first source/emitter follower transistor,
• means for generating current to an output node of the first source/emitter follower transistor, and
• means for filtering radio frequency signals at the output node of the first source/emitter follower transistor;
• and
• a power amplifier bias circuit stage coupled to the envelope detector circuit, the power amplifier bias circuit stage including:
• at least one replica transistor of the power amplifier,
• an envelope detector replica transistor, and
• a replica of the current generating means of the envelope detector circuit.

A method of biasing a power amplifier core stage of a power amplification device, comprising:

• adjusting a gain of a sensed radio frequency signal;
• generating an envelope tracking bias signal obtained at an output node of a source/emitter follower based envelope detector circuit, the envelope tracking bias signal based at least in part on the sensed radio frequency signal with the adjusted gain and a bias signal from a power amplifier bias circuit stage;
• and
• transmitting the envelope tracking bias signal to a power amplifier when the sensed radio frequency signal is applied to the source/emitter follower based envelope detector circuit.