| 摘要 |
PURPOSE:To reduce noise that could be generated from a transistor or the like by reducing current flowing between the collector and emitter of another transistor so as to reduce current consumption. CONSTITUTION:The levels of a stationary photocurrent and a signal photocurrent included in a current output from a light receiving element 1 are detected by a light level detection circuit C. When the level of the stationary light is judged to be low, a resistivity valuable circuit B is operated so that the collector resistance of a transistor R1 is increased. When the level of the signal light is judged to be high, the emission level of a light emitting element is lowered. Accordingly, the signal photocurrent included in the light receiving element is decreased and current flowing between the collector and emitter of a transistor T14 is also decreased. |
