A Doherty amplifier has different drain voltages applied to the power transistors of the main and peaking stages. The impedance inverter comprises at least one first series phase shifting element between the output of the main amplifier and the Doherty amplifier output and at least one second series phase shifting element between the output of the peaking amplifier and the Doherty amplifier output. This provides a wideband combiner. The combination of this wideband combiner and different drain drive levels provides an improved combination of efficiency and bandwidth.