A circuit input (IT) carrying an input signal to be detected having a dynamic signal range of, for example, the order of magnitude of 2000 is connected to a circuit output (OT) via a series arrangement of a filter circuit (F) and a rectifier circuit (PDR) and integration circuit (INT) of a specific design, for supplying a detection signal having a dynamic signal range in the order of magnitude of 100. To that end the rectifier circuit (PDR) comprises, interconnected in a junction point (P), a capacitor (C2), a leakage resistor (R14) and two rectifier transistors (T5, T6), as a result of which this circuit is basically operative as a peak detector. For an essential noise removal the junction point (P) is connected to a power supply terminal via an emitter-collector path of a biased transistor (T7). Furthermore the resettable integration circuit (INT) is given a non-linear, smoothed integration characteristic by biased diode-capacitor series arrangements (D1, C5, R18), (D2, D3, C6, R19).
Detection circuit for an auto-focusing system for an image pick-up device.