Signal level detector for compact disc player

Abstract

For detecting whether an input signal is above or below a reference level in such a way that brief signal interruptions and negative spurious pulses are not interpreted as decreases below the reference level, the detector includes an input comparator, a first delay circuit, a second delay circuit and an output circuit. The first delay circuit comprises a first integrator comprising a first transistor and a first capacitor, a first current source and a second comparator. The second delay circuit comprises a second integrator with a second transistor and a second capacitor, a second current source and a third comparator. The first delay circuit and the second delay circuit have equal delay times. In order to ensure that during detection of a decrease below the reference level a positive spurious pulse is not interpreted as an increase above the reference level a third Transistor connects a third current source in parallel with the first current source of the first delay circuit when the input signal lies below the reference level, so that the delay time of the first delay circuit becomes smaller than that of the second delay circuit.