| 摘要 |
PURPOSE:To prevent an operating device from malfunctioning by obtaining a constant current from a provided constant-current circuit and by driving a load with the constant current. CONSTITUTION:A control IC2 sends control pulses according to a prescribed program to exercise sequence control over stopping-down operation, mirror-up operation, etc., and also to perform arithmetic for the determination of exposure. A control pulse S operates a switching transistor 41 to drive a load 61. In this case, the load 61 is supplied with a constant current from a constant-current circuit 5. The base of a transistor (TR)10 constituting the constant-current circuit 5 is connected to the constant-voltage output terminal of the control IC2, and the collector to the switching circuit 4. Since the base voltage of the TR10 is held constant, the emitter current is held constant without reference to variations of a power voltage. This constitution prevents an operating device from malfunctioning. |
