| 摘要 |
PURPOSE:To increase the upper limit of a transmission band by detecting the peak level of a signal precedently even during the reception of the 1st signal pulse arriving after the continuous absence of a light signal, and setting a threshold voltage to the center of the signal. CONSTITUTION:A signal (f) generated by delaying the output of an amplifier 2 by a certain time through a delay circuit 16, e.g. delay line is applied to the other input of a comparing circuit 9. This delay time may be shorter than the rising time of a signal (a), so a large value corresponding to the rising time of a peak detecting circuit 3 which is 50-100ns is not required. The rise of the threshold voltage (e) coincides with the signal (a) before the delay, so a delay time DELTAt is so set that the threshold voltage (e) finishes rising before the delay signal (f) finishes rising. Namely, the threshold voltage (e) rises the delay time DELTAt earlier. Consequently, the threshold voltage can be discriminated in the center of the signal even at the rising of the 1st signal pulse, so a pulse having no distortion is outputted from the comparator 9. |
