Doherty Amplifier Circuit with Phase-Controlled Load Modulation

摘要

A symmetric Doherty amplifier includes a main amplifier and a peaking amplifier of the same size as the main amplifier. The symmetric Doherty amplifier is configured to operate at peak output power when the main amplifier and the peaking amplifier are each in saturation, and at output-back-off (OBO) when the main amplifier is in saturation and the peaking amplifier is not in saturation. Phase shift circuitry is configured to shift the phase at an output of the peaking amplifier at OBO so that a load impedance seen by the main amplifier and efficiency of the symmetric Doherty amplifier both increase at OBO as a function of the phase shift at the peaking amplifier output.