Patent ID: 7599734

Claim:
An electronic endoscope system comprising: a plurality of optical adaptors, each optical adaptor having at least two arrays of serially connected light-emitting elements serving as illuminating means; an insertion unit to which one of the optical adaptors is freely detachably attached at a distal portion thereof, the one of the optical adaptors being configured to be replaceable with another optical adaptor, the insertion unit including an electric cable inserted thereto and connected to the light-emitting elements; and a control unit having a constant-current circuit that sets, to be constant, the amount of current flowing to the light-emitting element via the electric cable, wherein the constant-current circuit includes a resistor having one end connected to the light-emitting elements and another end connected to a ground, a transistor connected between the resistor and the light-emitting elements, and an operational amplifier, a connecting point between the transistor and the resistor being connected to a negative input terminal of the operational amplifier, and wherein the constant-current circuit sets to be constant the amount of current flowing to the light-emitting elements in accordance with an amount of voltage inputted to a positive input terminal of the operational amplifier.