A Doherty amplifier including a carrier amplifier (Main), and at least one peaking amplifier (Peak), wherein an impedance inverter (6) at the output of the carrier amplifier includes first and second parallel paths, the first path (10) including a first λ/4 line impedance (L2a) providing an impedance inversion, and the second path (12) including a variable second impedance, including transmission line lengths (L2b, L3) and voltage controlled varactor devices (C1, C2) for adjustment of frequency response and/or output impedance of the impedance inversion means, in order to provide optimal impedance over a broadband range of frequencies.