Patent ID: 7295064

Claim:
A Doherty amplifier comprising: an input terminal; input branching circuit for distributing a signal applied from said input terminal to a first path and a second path; a carrier amplifier for amplifying a signal distributed to the first path by said input branching circuit; a peak amplifier for amplifying a signal of a predetermined level or higher among signals distributed to the second path by said input branching circuit; output combining circuit for combining an output of said carrier amplifier with an output of said peak amplifier; and a gain compensator disposed at a position ahead of said peak amplifier in the second path for changing a gain in accordance with the level of an input signal in order to correct the level of the signal distributed to the second path, said carrier amplifier and said peak amplifier being devices having the same characteristics, said peak amplifier having a gain smaller than an ideal gain, wherein said gain compensator has a larger gain, when a signal equal to or higher than the predetermined level is applied, than a gain when a signal lower than the predetermined level is applied, said gain being set based on a transfer conductance of said peak amplifier, and said gain compensator comprises a parallel circuit comprising an anti-parallel diode and a resistor, or a parallel circuit comprising a diode and a resistor, or a FET, or a bipolar transistor.