摘要:
A reference voltage generating circuit (9) for supplying a reference voltage (Vag.+-..DELTA.V) is connected to a peak hold or tracking circuit (34). The setting value of the voltage (.DELTA.V) is determined to a value exceeding the minute voltage fluctuations, such as back pulses or noises, occasionally contained in the input signal (Vin), by the voltage division in the generating circuit (9). Therefore, in response to the input signal Vin in accordance with the alternate mark inversion, exact data which is not influenced by the minute voltage fluctuation can be detected by the data detector (33).