An amplifier circuit (100) comprises three amplifier subcircuits (121,131,141) connected via a network of transmission lines to a common node. A control circuit is configured to control the three amplifier subcircuits (121,131,141) to operate in first, second, and third operating modes, such that a first subcircuit (121) is active in the first, second, and third modes, a second sub-circuit (141) is inactive in the first mode but active in the second and third modes, and a third subcircuit (131) is inactive in the first and second modes but active in the third. A quarter-wavelength transmission line (170) couples the output node of the second sub circuit (141) to the output node (160) of the third subcircuit (131).
