Patent ID: 8441321

Claim:
A multi-stage amplifier structure, comprising: a first branch connected to an output node, said first branch including two transistor amplifiers, wherein outputs of the two transistor amplifiers are connected to one another with a quarter wavelength transmission line or circuit equivalent of a quarter wavelength transmission line, wherein the two transistor amplifiers of the first branch comprise, an inner transistor amplifier, the output of which is connected to the output node by a partial wavelength transmission line, and an outer transistor amplifier, the output of which is connected to said inner transistor amplifier by said quarter wavelength transmission line or said circuit equivalent; and a second branch including at least one further transistor amplifier, an output of which is connected to said output node, said second branch including a partial wavelength transmission line, or circuit equivalent of said partial wavelength transmission line, connected between the output of the further transistor amplifier and the output node wherein the second branch comprises, an inner transistor amplifier comprising said further transistor amplifier connected to said output node by said partial wavelength transmission line, and an outer transistor amplifier, the output of which is connected to the output of said inner transistor amplifier by a second quarter wavelength transmission line or circuit equivalent of a quarter wavelength transmission line; wherein the multi-stage amplifier structure is configured such that Chireix action takes place between at least one of said transistor amplifiers in the first branch and the at least one further transistor amplifier in the second branch.