Abstract: The invention relates to an infrared gas sensor with an energy supply apparatus for operating at least one radiation source with current or voltage pulses, with at least one measurement area disposed in the beam path, with at least one wavelength-selecting element, with at least one detector element emitting an electrical measurement signal and with a switching device (3) to control the pulse duration of the current or voltage pulses. The switching device (3) has means for setting the pulse duration in such a way that the current or voltage pulse is so turned off that the required pulse duration is smaller than that required to reach the maximum (&tgr;max) of the at least one measurement signal of the at least one detector element.