an amplifier includes a main amplifier circuit with an input and output . at least one auxiliary amplifier circuit has an input and output , and is selectively operable to operate in combination with the main amplifier circuit . a signal combining network is coupled with outputs of the main amplifier circuit and auxiliary amplifier circuit and is operable to combine amplifier circuit output signals at an output port . the main and auxiliary amplifier circuits operate in an operational frequency band , and a delay element is coupled to the input of the auxiliary amplifier to introduce a delay to that input that is configured for introducing a delay that is an integer multiple of a wavelength at a frequency within the operational frequency band .