Patent ID: 8234907

Claim:
A photo acoustic detector for detecting a concentration of a sample in a sample mixture, the photo acoustic detector comprising: a light source for producing a light beam for exciting molecules of the sample, a light modulator for modulating the light beam for generating pressure variations in the sample mixture, an amplitude of the pressure variations being a measure of the concentration, a detector element for converting the pressure variations into a detector current, and a processing section for processing the detector current to generate an output signal representing the concentration, wherein the processing section comprises: an integrating amplifier for integrating the detector current, the integrating amplifier being coupled to the detector element via a hold switch, and a timing circuit for generating a hold signal, SWHOLD, for operating the hold switch in order to couple the integrating amplifier to the detector element during a predetermined interval of a period of the detector current, wherein the predetermined interval is shorter than the period of the detector current.