| 摘要 |
PURPOSE:To make removal of background light and dark current possible by connecting two light receiving diodes having the same characteristics in series, impressing DC bias voltage to both ends, and making voltage at the middle point between the two light receiving diodes output. CONSTITUTION:The N area of a light receiving diode 11 is grounded and the P area is connected to the N area of a light receiving diode 12. A terminal 15 is connected to the P area of the light receiving diode 12 and negative bias voltage VB is impressed. A terminal 16 is the middle point of connection between the two light receiving diodes 11, 12, and an output voltage V0 is outputted. Background light 13 enters the light receiving diode 11, and current JB is flowed thereby. Signal light 14 enters the light receiving diode 12 and current JS is flowed thereby. However, as the two light receiving diodes are connected in series, JS becomes equal to JB. Thus, a signal corresponding to the difference of quantity of light of the two light receiving diodes can be taken out as voltage, and the influences of background light and dark current can be eliminated.
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