The invention relates to circuit arrangements for operating lamps and to operating devices which contain such circuit arrangements. A first stage of a circuit arrangement according to the invention comprises a SEPIC known from the literature. The SEPIC provides a DC voltage which an inverter converts to a radiofrequency AC voltage for lamp operation. According to the invention, an electronic switch (S1) acts both in the SEPIC and in the inverter. Two diodes (D1, D2), which are connected into the supply line for the electronic switch (S1), prevent the SEPIC and the inverter from influencing one another.