PURPOSE: To reproduce a digital signal stably, by comparing an FM demodulation signal of a frequency-modulated digital signal, which is reproduced from a recording medium, and the DC level of the FM demodulation signal with each other in level.
CONSTITUTION: The reproduced frequency-modulated digital signal taken out from a pickup circuit 19 is supplied to a limitter and FM demodulator 20 and has the amplitude variation eliminated and is subjected to FM demodulation. This FM demodulation signal is branched off in two directions, and one is converted to a cosine square wave by a low-pass filter 21 and has DC components stopped in a circuit consisting of a DC stopping capacitor C1 and a resistance R1 and is impressed to an inverted input terminal of a comparator 25, and the other passes through an amplifier 22, an integration circuit 23, a DC amplifier 24, and a resistance voltage dividing circuit consisting of resistances R4 and R5 and is impressed to a non-inverted input terminal of the comparator 25.
NISHIKAWA KAZUNORI
IWASAKI YOSHIKI
FURUMURA MAKOTO
UENO SHIYOUJI
