| 摘要 |
PURPOSE:To perform stable, high-precision detection by providing a constant current circuit to a voltage drop element in a constant voltage circuit in a detector which compares the oscillation output voltage of an oscillation circuit which varies in oscillation intensity according to the amount of the magnetic developer in a container with a reference voltage and deciding on the remaining amount of the developer. CONSTITUTION:The constant voltage circuit 13 which stabilizes a DC voltage supplied from a DC power source 10 to the oscillation circuit 7 has a Zener diode 16 connected in parallel between power source lines 14 and 15 to the oscillation circuit 7 and a field effect transistor (FET) 17 inserted as the voltage drop element in parallel to the power source line 14. The emitter of this FET 17 is connected to the load-side base to have constant current characteristics by saturation characteristics. A constant current ID by the saturation characteristics of the FET 17 is divided into the supply current IOSC to the oscillation circuit 7 and the operating current IZ of the Zener diode 16. The oscillation output voltage VO of the oscillation circuit 7 is stable againt temperature variation and a secular change. |
