PURPOSE: To suppress a deterioration due to inter-code interference by inserting a waveform shaping circuit between an equalizing amplifier and an identification circuit and using the waveform shaping circuit to shape a waveform suitable for the identification circuit.
CONSTITUTION: When an equalized waveform is inputted to a gate of a FET 31, a drain current flows by a supply voltage Vcc between a drain source and a gate bias to cause a voltage drop across a source resistor 35. When the voltage drop exceeds the pinch-off voltage of the FET 31, no amplification is applied for the period and the FET 31 is cut off and a waveform with a small amplitude is obtained. However, the rising of the waveform is made steeper for the part. Since a part of the drain output amplified by the FET 31 in a 2nd stage FET 32 exceeds the pinch-off voltage of the FET 32, only the part is not amplified bus cut off. Thus, the upper/lower unsharpened parts are removed in the input waveform in the process of amplification and the waveform is made steep, then the deterioration due to inter-code interference is suppressed.
OKIYAMA TADASHI
ARAI YASUNARI
