EMS tests are performed with different types of RF signals ranging from narrow band to broadband. The interference signals have different modulation characteristics and can consist of multiple tones or even band limited noise which has implications for the selection of a suitable amplifier. This presentation covers the most common types of interference signal and also new developments from an EMC standards point of view. Which amplifier parameters to look for and how they are specified, will also be covered simplify comparing the different amplifier possibilities.