In various embodiments, a dimmable operating device for the combined operation of a gas discharge lamp and a semiconductor light source is provided. The dimmable operating device may be configured such that only the semiconductor light source is operated in the lower dimming range and only the gas discharge lamp is operated in the upper dimming range, and at the changeover points at which one sort of light source out of the semiconductor light source and the gas discharge lamp is switched off or on, at the same time a jump in power is applied to the other light source out of the semiconductor light source and the gas discharge lamp, with the result that the human eye cannot perceive, or can only perceive with difficulty, the changeover point.