| 摘要 |
PURPOSE:To make it possible to operate the titled circuit up to a lower voltage area by connecting a diode from a node between a resistor and a diode in a serial circuit for supplying a current from a power supply on the high voltage side to a constant voltage diode to the low voltage side in the forward direction. CONSTITUTION:A control transistor (Tr)Q21 is actuated by a base current supplied from an error amplifier TrQ22. A diode D21 is connected from the node of a resistor R26 and a diode D22 constituting a serial circuit for supplying a current from a high voltage side input terminal (23) to a constant voltage diode DZ21 to the low voltage side input terminal in the forward direction. When the voltage of input power becomes almost equal to a reference voltage in said constitution, current starts to flow into the D21 through the R26. When the base potential of the TrQ22 starts to drop together with the input voltage, the TrQ22 is prevented from cutoff because of the formation of the D21, D22. Namely, the TrQ21 also is kept at conductive state and the circuit can be operated up to a lower voltage area. |
