CONSTANT-CURRENT CIRCUIT

PURPOSE:To constitute the circuit so that an output current is not varied even in the case there is a temperature fluctuation by connecting a circuit for connecting in series a second PN junction element and a second resistance in parallel to a first resistance. CONSTITUTION:Between a positive voltage source V1 and a ground point, a series circuit of a resistance R1 and diodes D1, D2 is inserted, and to a connecting point (a) of the resistance R1 and the diode D1, a base of an NPN transistor Q1 is connected. Also, its collector is connected to a current output terminal T1, its emitter is grounded through a resistance R2, and also, between the emitter and a ground, a series circuit of a diode D3 and a resistance R3 is inserted. In such a way, to an output current, a current component having a positive temperature coefficient is added, in addition to a current component having a negative temperature coefficient. Accordingly, the circuit can be formed as a constant-current circuit which is not influenced by a variation of an ambient temperature even in a place in which a temperature is varied remarkably.