A circuit arrangement comprises a photo detector (2) for detecting electromagnetic energy and a signal generating means (4, 6, 12, 16) being suitable for generating a sequence of events wherein an event interval of the sequence depends on the detected electromagnetic energy. The signal generating means (4, 6, 12, 16) is coupled downstream of the photo detector (2). A counting means (30, 32, 34, 36) for measuring a time period until a given number of events has been generated is coupled downstream of the signal generating means (4, 6, 12, 16).