| 摘要 |
PURPOSE:To widen the dynamic range of optical reception power with simple configuration by using a mean value of binary potential corresponding to a logic level of an output signal of a preamplifier for a reference potential of a discrimination circuit. CONSTITUTION:Lets points representing a source potential of a FET 21, an anode potential of a diode D1, and a cathode potential of a diode D2 be respectively points A, B, C. When an input signal is at an H level and a reference circuit starts its operation, the potential at the points B, C is once converged to a potential of the point A once (referred to as VH). When the input signal changes from H to L, the potential at the point A (referred to as VL) is reduced. In this case, a reverse bias is applied to the diode D2 at H level detection side and the potential at the point C is kept to the level VH. On the other hand, when the potential at the point A decreased from the VH to the VL, a forward bias is applied to the diode D1 and the potential at the point B is converged to the VL. Since the input resistance of the FET is large, the points B, C keep a binary potential corresponding to the logic level of the output signal of the preamplifier. |
