Multi-mode power amplifier with high efficiency under backoff operation

Abstract

A multi-mode RF amplifier is disclosed having high and low output power modes and two power paths. A first RF amplifier delivers power to both paths. When the multi-mode RF amplifier is biased into the high power, HP, mode, substantial power is delivered via both (first and second) paths. While in the low power, LP, mode, an RF switch is turned off, creating a high input impedance, open circuit for the first path, and effectively isolating the two paths. Therefore, power is delivered by the first RF amplifier to the second path only. The impedance presented to the output of the first RF amplifier is equal to the input impedance of the second path which may be optimally set for maximizing power added efficiency or output power in LP mode. Note that, in a preferred embodiment, even in the HP mode more power is delivered to the second power path than to the first power path.

Dependencies are inferred from the claim text.