An amplifier for an input signal Sin, present at an input terminal, with a gain factor adjustable by a control terminal, so as to provide the amplified input signal Sin′ at an output terminal. A decoupler is connected to the amplifier on the output side and provides a decoupling signal Sactual which depends on the amplified input signal Sin′. The decoupling signal Sactual is processed in an analog manner, and a prepared signal Sactual′ is provided which is a measure of the actual output power. Comparing the prepared signal Sactual′ to a target value Starget in an analog manner yields a comparison signal Scontrol controlling the gain factor, and a target value Starget is a measure of the target power of the amplified input signal Sin′. The processor is implemented to create a predetermined ratio between the target power and the actual power.