According to an embodiment, a method is provided that includes: adapting the impedance of the load dependent on working conditions of the active device using a controllable output-side adaptation network coupled between an output-side terminal of a transformer and an output-side node, to generate an adapted impedance of the load, adjusting the adapted impedance independent of the working conditions of the active device, using the transformer including a first inductor having a first terminal to receive the output of the active device via the input-side node, a second inductor having an output-side terminal, where the second inductor is magnetically coupled to the first inductor.