| 摘要 |
PURPOSE:To remove the variation of an amplification factor for pulse light and to improve SN ratio, by forming the titled circuit by a parallel circuit consisting of a transistor, a photodiode and a resistor and a capacitor. CONSTITUTION:The titled circuit is provided with the parallel circuit consisting of the photodiode 7 connected to the base of the transistor TR1 and the resistor 6 and the capacitor 8 connected to a connection point different from the base of the TR1. In said circuit, the DC component of optical current ordinally generated in the photodiode 7 by disturbance light is made flow into the resistor 6 and scarcely flows into the TR1. Therefore the bias point of the TR1 is not changed. On the other hand, the AC component of optical current generated in the photodiode 7 by pulse light is made flow into the TR1 through the capacitor 8. Thus the TR1 is prevented from bias change due to disturbance light, making it possible to reduce the change of the amplification factor for pulse light and improve the S/N. |
