| 摘要 |
PURPOSE:To obtain a satisfactory threshold voltage without being affected by the fluctuation of temperature and a source voltage and to dispense with adjustment for an external threshold value by providing a threshold value generation circuit between the positive phase signal and the negative phase signal of the output of a light receiving amplifier circuit. CONSTITUTION:A received optical signal is converted to a current by a photodetector 1, and an electrical signal is outputted differentially as an output DC offet voltage, a positive phase side output signal, and a negative phase side output signal by the light reception amplifier circuit 2. When the resistance values of a resistor 10 and a resistor 11 comprising the threshold value generation circuit 9 are set at the same resistance values, a voltage Vref generated from the connection point of the resistors 10, 11 goes to the 1/2 of the sum of a positive phase side DC voltage V2 and a negative phase side DC voltage V1, thereby, the optimum threshold voltage with amplitude of half the output amplitude can always be generated. Thereby, it is possible to obtain the satisfactory threshold voltage not being affected by the fluctuation of the temperature and the source voltage, and also, to dispense with the adjustment for the external threshold value at every time of manufacturing, and to reduce a production cost. |
