Patent ID: 6784724
Filing Date: 2004-08-31
Classification: G05F

Abstract:
A constant voltage generating circuit comprising:a band gap circuit of which an output voltage is so controlled, with a power supply voltage being supplied, as to be a predetermined constant voltage, as a result of a predetermined current level flowing therethrough, and a first transistor that effects negative current feedback when the output voltage reaches the predetermined constant voltage so that current flowing through the band-gap circuit is so controlled as to be the predetermined current level, wherein the constant voltage generating circuit further comprises: a second transistor having a base and an emitter thereof connected to a base and an emitter of the first transistor respectively, the second transistor that, when current associated with said negative current feedback flows through the first transistor, controls the current flowing through the band-gap circuit so as to be the predetermined current level by negatively feeding back a current proportional to the current flowing through the first transistor; a resistor arranged in a current pass through which current flowing through the second transistor flows, the resistor generating a voltage drop thereacross when the current proportional to the current flowing through the first transistor and negatively fed back flows therethrough; and a starting signal output circuit that detects the voltage drop generated across the resistor to output a starting signal indicating that the output voltage reaches the predetermined constant voltage, wherein the emitters of the first and second transistors are connected to a band-gap voltage generated by the band-gap circuit so that the current flowing through the first transistor and the current flowing through the second transistor are negatively fed back to the band-gap circuit.