| 摘要 |
PURPOSE:To generate an output of a correct pulse width even with fluctuated optical input, to reduce the effect of a guard voltage and to output the correct pulse width even to a minute signal, by setting a discriminating level of a comparison circuit to a half the amplitude of an output signal of an amplifier at all times. CONSTITUTION:An optical signal is received at a photodetector 1, and a peak value Vp of an output signal A from the detector 1 is inputted to a comparison circuit 3 and a differential amplifier 6 of a peak value detecting circuit 5. Further, resistors 8 and 9 with equal resistance value are connected between a reference voltage circuit 4, which supplies a reference voltage to the amplifier 6 and the comparison circuit 3, and the amplifier 6, and a connecting point of the resistors 8 and 9 is connected to a reference voltage input terminal of the comparison circuit 3. A prescribed current flows to the resistors 8 and 9 from a constant current source 10 connected to the output terminal of the circuit 5, and the output voltage of the circuit 4 is made equal to a DC output voltage Vo of an amplifier 2 at no signal. The discriminating level of the comparison circuit 3 is always taken as a half the amplitude of an output signal of the amplifier 2, the effect of a guard voltage Vg is reduced and a correct pulse width is always outputted. |
