| 摘要 |
PROBLEM TO BE SOLVED: To provide a fixed discrimination optical reception circuit which can resist to the variation of external conditions, such as the operating voltage, power supply voltages, the ambient temperature, and, at the same time, can realize low power consumption at low cost. SOLUTION: An optical reception circuit which inputs a current signal outputted from a photodetector 12 correspondingly to a received optical signal 11 and a control current which stipulates the discriminating level from a current source 14 controlled by means of a current control circuit 13 to a discriminator 23 after converting the signal and current into a voltage signals by means of trans-impedance amplifiers 21 and 22, respectively, and reproduces the pulse waveforms of the voltage signals by discriminating the logical levels of the voltage signals by means of the discriminator 23. In the optical reception circuit, logical constitutions of the two amplifiers 21 and 22 are made the same and the size of each transistor in the amplifier 21 is made n-times as large as that of the corresponding transistor in the amplifier 22. In addition, the impedance of the passive element in the amplifier 21 is made 1/n as small as that of the passive element in the amplifier 22. |
