CONSTANT VOLTAGE CIRCUIT

PROBLEM TO BE SOLVED: To provide a constant voltage circuit capable of preventing unstable circuit operation while maintaining output voltage quality for a wide range of operation conditions. SOLUTION: In the constant voltage circuit of which a series regulator consists of a control transistor Q1 and error amplifier 3, a phase compensation transistor C1 is connected between a non-inverted input terminal (+) of the error amplifier 3 and source of a supplementary transistor Q2 for simultaneously operating with the control transistor Q1. Between the phase compensation transistor C1 and source of the control transistor Q1, a correction circuit 5a for changing impedance according to operation condition of the constant voltage circuit. By utilizing the impedance change of the correction circuit 5a, appropriate phase correction is realized and operation of the constant voltage circuit is stabilized even under a condition that the operation is easy to lose stability. COPYRIGHT: (C)2004,JPO