POWER AMPLIFIER FOR EFFICIENTLY AMPLIFYING LINEARLY MODULATED SIGNALS

摘要

A power amplifier includes a carrier amplifier path and a peaking amplifier path. The carrier amplifier path includes a carrier amplifier (208), and an impedance transforming network (214). The peaking amplifier path includes a peaking amplifier (210), an impedance transforming network (216), and a phase delay quarter wave element (226). The arrangement forms an inverted Doherty combiner where as the nominal impedance at a summing node (230) increases with increased conduction from the peaking amplifier, the load impedance at the output of the carrier amplifier decreases so as to maintain the carrier amplifier at a saturation point as the input signal (232) increases, and results in a reduction of the number of phase delay elements needed over a conventional Doherty approach. In a preferred embodiment the carrier and peaking amplifiers consist of cascaded stages, and are disposed on a common integrated circuit die (304). The impedance transforming networks and phase delay element are disposed on a common substrate (306), as is an input splitter network (308).