Patent ID: 7332957

Claim:
A constant current circuit that generates a constant output current corresponding to an input voltage, comprising: a differential amplifying unit to which the input voltage and a feedback voltage to be compared therewith are applied, the differential amplifying unit outputting a differential voltage between the input voltage and the feedback voltage; a first transistor with a first control electrode to which the differential voltage is applied; a first diode element that is connected to a power-supply side electrode of the first transistor; one or a plurality of second transistors that generates the output current duplicated from a diode current by applying to a second control electrode a voltage drop in the first diode element developed as a result of the diode current flowing through the first diode element due to drive of the first transistor; a feedback voltage conversion block that converts the duplicated current of the diode current flowing through the second transistor into the feedback voltage, which is fed back to the differential amplifying unit; and a constant current loading unit that is connected to a ground side electrode of the first transistor, the constant current loading unit making a voltage change in the ground side electrode follow a voltage change in the first control electrode, the constant current loading unit acting as a constant current load on the ground side of the first transistor.