Apparatus and method for efficiently amplifying wideband envelope signals

An amplifier circuit for amplifying an input signal, comprising:

• an AB-type RF amplifier having an input and an output, the input configured to receive the RF input signal;
• a synchronous buck DC/DC converter having an input and an output,
• a positive feedback loop coupled between the output of the amplifier and the input of the converter;
• and
• a resistive load coupled in parallel between the respective outputs of the amplifier and converter.

An amplifier circuit for amplifying an input signal, comprising:

• a dependent voltage source that operates at a first bandwidth and a first power efficiency, the voltage source configured for generating a first voltage that varies with the input signal, and a first current;
• a current source that operates at a second bandwidth narrower than the first bandwidth, and a second power efficiency greater than the first power efficiency, the current source configured for generating a second current that varies with the first current, and a second voltage;
• and
• a load coupled in parallel between the voltage source and current source, wherein the first voltage appears across the load, and the first and second currents flow through the load.