| 摘要 |
PURPOSE:To attain one chip circuit integration up to a signal processing section including a photodetector by providing a head amplifier, a dummy amplifier, a detection section, a differential amplifier and a comparator. CONSTITUTION:The dummy amplifier 2 having a constitution symmtrical to the 1st stage head amplifier 1, a peak detection section 3 detects a peak value of a head, the dummy amplifier 2 and the peak detection section 3 form an intermediate value of the head amplifier amplitude and the differential amplifier 5 receives the intermediate value and the output of the head amplifier 1 as the optical ATC circuit, and the comparator 7 binary-codes the output of the ATC circuit and the reference potential. Since the variation of the bias is expected for the ATC circuit and the reference potential to some degree, hysteresis is provided to the comparator 7. Thus, even when a mean value detection section 4 generating the reference potential of the comparator uses an externally mounted capacitor, a complete one chip integration is attained. |
