| 摘要 |
PURPOSE:To obtain a detection signal at a collector by applying a detected voltage to an emitter of a transistor (TR) and inserting a constant voltage diode between the base and common so as to turn off the TR when an emitter voltage is low and to turn on the TR when the emitter voltage gets higher than a prescribed voltage or over decided by the constant voltage diode. CONSTITUTION:When the emitter voltage is low, the TR2 is turned off and the collector voltage is OV. When the emitter voltage rises and when it exceeds a sum VSH between a Zener voltage VZ of the constant voltage diode D1 and a base-emitter voltage VBE of the TR, the base current of the TR2 starts flowing and the TR2 is turned on and almost the same voltage as the emitter appears at the collector. When the input voltage is the VSH or below, the collector voltage is nearly 0 and when the input voltage is more than the VSH, the collector voltage is nearly equal to the input voltage and a detection signal is obtained. |
