CONSTANT CURRENT CIRCUIT

摘要

A constant current circuit (1) is provided with: a first current path in which a current flows from one end of a resistor (R1) and through a resistor (R4) and the collector and emitter of a bipolar transistor (20) in that order; and a second current path in which current flows from outside through an input terminal (T1) and through the collector and emitter of a bipolar transistor (21) in that order. Through the second current path flows a current having a value that is a prescribed number of times greater than the current flowing through the first current path. A microcomputer (10) adjusts the potential on one end of the resistors (R2, R3), respectively, or opens one end up so as to change the amount (Iref) of current flowing through the first current path.