| 摘要 |
PURPOSE:To attain waveform shaping while excluding the effect of noise effectively even when an input signal level is decreased by referencing a reference voltage corresponding to an input signal level so as to shape the waveform. CONSTITUTION:An optical signal inputted to a photodetector PD is amplified by a preamplifier IC1 connecting to a feedback resistor Rr, and reaches an IC2 being an output buffer through a circuit 2 whose transfer function is H(S). On the other hand, when an optical current flows to the photodetector PD, a voltage is generated across a resistor R1, the voltage connects to an inverting input of an amplifier IC3 and the amplifier IC3 supplies an output corresponding to the generated voltage to a noninverting input of the IC2. Thus, the level is changed in response to the light receiving power so as to be in the middle of the amplitude of the signal voltage given to the inverting input of the IC2. Thus, the effect of noise caused around 'H' level and 'L' level is hardly caused and the reception sensitivity is substantially improved. |
