The invention relates to high power radiofrequency amplifiers, in particular to amplifiers having output impedance matching networks, exemplary embodiments of which include a radiofrequency amplifier having an active device mounted on a substrate within a device package, the amplifier having an output impedance matching network comprising a high pass network provided at least partly on the active device and a low pass network having a first inductive shunt connection between an output of the active device and a first output lead and a second inductive shunt connection between the output of the active device and a second output lead, wherein part of the second output lead forms an inductance contributing to the inductance of the low pass network.