Patent ID: 7301395

Claim:
A Doherty amplifier comprising: a power splitter having a first output and a second output, wherein the first output is connected to a main power splitter having first and second outputs which differ in phase by 90°; and the second output is connected to an auxiliary power splitter having first and second outputs which differ in phase by 90°; a main final stage amplifier comprising first and second main paired amplifiers, the inputs of which are connected to the first and second outputs of the main power splitter; an auxiliary final stage amplifier comprising first and second auxiliary paired amplifiers, the inputs of which are connected to the first and second outputs of the auxiliary power splitter; wherein the output from the first main paired amplifier is connected to the output from the first auxiliary paired amplifier by an impedance inverter; and the output from the second main paired amplifier is connected to the output from the second auxiliary paired amplifier by an impedance inverter; the amplifier being arranged such that a relative phase shift is introduced to the signals input to the main and auxiliary power splitters to offset the phase shift of the impedance inverters.