CONSTANT-CURRENT CIRCUIT

PURPOSE:To constitute the circuit so that a variation of an output current is suppressed small even in the case a fluctuation occurs in a current voltage by bringing a part of the output current to feedback and supplying it. CONSTITUTION:A positive voltage source V1 is connected to a current supply terminal T2 of a current mirror CM, and also, connected to an output terminal T4 of the current mirror CM and bases of transistors Q3, Q1 through a resistance R3, and moreover, grounded through diodes D1, D2. Also, an input terminal T3 is connected to a collector of a transistor Q3, and its emitter is grounded through a resistance R4. A collector of the transistor Q1 is connected to an output terminal T1, and its emitter is grounded through a resistance R2. In such a way, a current output terminal of the current mirror CM is connected one terminal of a PN junction element as a current supply means to the PN junction element. In such a way, even in the case a fluctuation of a power supply voltage occurs, a variation of an output current is suppressed small.