| 摘要 |
PURPOSE:To increase the temperature stability, by minimizing factors to bias fluctuation and giving the reproducibility to the fluctuation. CONSTITUTION:A DC bias of an output point (emitter of an emitter follower Q3) when an optical signal is not inputted from a photodiode PD is 2VBE+VOF. When the optical signal is inputted, the potential at this point is lowered by Vp to be 2VBE+VOF-Vp. When this output passes through a circuit consisting of an emitter follower Q10 and a transistor (TR)Q11 with common emitter, the potential becomes the VOF with no optical signal and VOF-Vp with the optical signal. Thus, the collector voltage of the TRQ11 can be represented with the parameter only without temperature dependancy and the high temperature stability can be achieved. The output of the TRQ11 is inputted to one input of a comparator CM, to which an average value of the output of the TRQ11 is applied as a reference input, allowing to achieve an output of ''H'' level or ''L'' level. |
