The application relates to transmission power control in transmission systems, in particular mobile radio systems. One object of the invention is to indicate a way of guaranteeing, compared with the state of the art, improved, in particular dynamic, control of transmission powers within predefinable emitted interference requirements with, in particular, increased efficiency and reduced power consumption. For this purpose, the invention provides for the filtering of an amplified transmission signal to be divided up between a narrower-band tunable pre-filter (4) and a broadband post-filter (10). To perform this operation, a signal-amplification circuit is proposed which comprises a tunable filter (4) which is connected downstream of a power amplifier (2).