High efficiency power amplifier using combined linear and switching techniques with novel feedback system

A radio transmitter, comprising:

• a power supply reference generator for generating a reference signal;
• an amplifier apparatus coupled to the power supply reference generator for generating an output signal that tracks the reference signal;
• a radio frequency (RF) power amplifier coupled to the amplifier apparatus for amplifying an RF signal, the RF power amplifier powered by the output signal of the amplifier apparatus and producing an amplified RF signal;
• and
• an RF source for generating the RF signal,
• wherein the amplifier apparatus comprises:
• an output node having an output voltage;
• a switching amplifier having a first output coupled to the output node for delivering a switching amplifier output current to the output node;
• a modulator coupled to the switching amplifier for controlling the switching amplifier;
• a linear amplifier producing a linear amplifier output current through a second output coupled to the output node;
• and
• a feedback network coupled to the modulator for controlling the modulator, the feedback network also coupled to the reference signal, which the amplifier apparatus tracks, the feedback network further coupled to a current sense signal proportional to the linear amplifier output current, and coupled to a switching amplifier signal internal to the switching amplifier, the switching amplifier signal not derived from the output voltage and not generated by sensing the switching amplifier output current.