| 摘要 |
PURPOSE:To detect an original or turning off of a fluorescent lamp accurately by a simple circuit, by performing said detection by the amplification output of an operational amplifier which has sufficiently low output impedance. CONSTITUTION:A reference photoelectric converting element C1, a photoelectric converting element C2 for original detection, reference power sources B1, B2 and B3, and operational amplifiers 6, 7 and 9, etc., are provided. A voltage divided through the output feedback photoelectric converting element and a resistor R1 is applied to the inverted-input terminal of the amplifier 6. On the other hand, output of the amplifier 6 is applied to the inverted-input terminal of the amplifier 7 after voltage division through the converting element C2 and a resistance R2. Consequently, the output of the amplifier 7 is used to detect an original 1 entering and a fluorescent lamp 3 is being turned off. |
