| 摘要 |
PURPOSE:To keep a current limit value constant by regulating an emitter potential of a limit transistor(TR) whose base potential is decided based on a detection current being 1/N of a current flowing to an output TR to a constant value based on a constant current extracted from a constant current path of a band gap type constant voltage circuit. CONSTITUTION:A constant current flowing to a collector of a TR Q21 in a constant current path of a band gap type constant voltage circuit is reflected by a current mirror circuit comprising PNP TRs Q27, Q28 and fed to a resistor R28 and the voltage drop across the resistor R28 decides the emitter voltage of the TR Q24. Thus, a current IC(Q21) flowing to the TR Q21 is independent of the output voltage V0 and the voltage drop across the resistor R28 is independent of the output voltage V0. Thus, even when an output voltage is made variable, the current limit is kept constant without any change. |
