DROP-OUT DETECTING CIRCUIT

PROBLEM TO BE SOLVED: To provide a detecting circuit whereby drop-out is compensated regardless of the size of the amplitude of a reproduction RF signal by providing a comparator(COMP) where the synthetic voltage of the voltage of a rectifying circuit with a long time constant with a D.C. reference voltage and the voltage of the rectifying circuit with a short time constant are inputted. SOLUTION: The reproduction RF signal from a recording medium is amplified and inputted to the two rectifying circuits with different time constants. In the rectifying circuit D2 with the long time constant, the D.C. reference voltage Vref is synthesized with a rectifying voltage via a resistor R4 so as to generate a synthetic voltage VTh. In the rectifying circuit D1 with the short time constant, the rectifying voltage V1 is generated. The both voltages are inputted to a comparator(COMP). A drop-out detecting signal(DOS) outputted from COMP, DOS is normally outputted when he amplitude of the RF signal is large. When amplitude is small, the synthetic voltage VTh is elevated, compensated to output the DOS.