| 摘要 |
PURPOSE:To simplify the constitution of a circuit which detects the drop of the input voltage by using a current mirror circuit to detect and compare the base current of a control transistor constituting a voltage stabilizing circuit. CONSTITUTION:A current mirror circuit consisting of transistors (TR) Q3 and Q8, resistances R1 and R2 and TRs Q4 and Q5 and another current mirror circuit consisting of TRs Q6 and Q7 are provided to a power supply voltage stabilizing circuit containing an error voltage amplifying circuit 1, a start-up circuit 2, a reference voltage generator 3, etc. The base current of a TRQ1 is detected by a current mirror circuit consisting of TRs Q2 and Q3, and the TRQ8 is turned on and off in accordance with the difference between the base current of the TRQ1 and the collector current of the TRQ7. Then a low level of voltage can be detected by the collector voltage V3 of the TRQ8. The collector current I1 of the TRQ7 is varied with variation of the resistance R1. Then the detection current value can be varied for the base current of the TRQ1. |
