| 摘要 |
PURPOSE:To obtain the output voltage which is stable even with the voltage variance of a battery power supply by using a transistor TR having its emitter end connected to an output line and then setting a Zener diode between the base end of the TR and the earth. CONSTITUTION:A fixed current iR decided by the diodes D1 and D2, a resistance R2 and a transistor TR1 is supplied to a Zener diode ZD1. Then the value VZD1-VBE2 obtained by subtracting the base-emitter voltage VBE2 of a TR2 from the Zener voltage VZD1 of the diode ZD1 is equal to the output voltage V0. Here the current iR is defined as iR=(VD1+VD2-VBE2)R2, where the forward voltage drops of the diodes D1 and D2 are referred to as VD1 and VD2 together with the base-emitter voltage of the TR1 defined as VBE1 respectively. Therefore a constant current is always supplied to the diode ZD1 despite the variance of the battery voltage. This secures the fixed level of voltage VZD1, thereby stabilizes the output voltage V0.
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