| 摘要 |
PURPOSE:To obtain proper exposure at all times by providing a signal generating circuit to change an input signal to a discriminating circuit and operating the generating circuit to change the driving speed a diaphragm. CONSTITUTION:Operational amplifiers 6, 10, 16 are connected in parallel to power sources 1, 2 connected in series. The non-inversion input terminal of the operational amplifier 6 is connected to connecting points of the power sources 1, 2 and the inversion input terminal is connected through a photoelectric element 4. A resistance 5 is connected between the output terminal and input terminal. Thus, a light measuring circuit that works as a photoelectric conversion amplifier which converts light entered through the diaphragm blade 3 placed in front of the photo-electric element 4 to voltage proportional to the intensity of light is formed by these devices 4, 5, 6. The non-inversion input terminal of the operational amplifier 10 is connected to the sliding piece 8a of a variable resistance 8, and the inversion input terminal is connected to the output terminal of the operational amplifier 10 and a discriminating circuit is formed by the variable resistance 8, resistance 9 and operational amplifier 10.
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