An operating circuit applied to a backlight includes at least one current control circuit, where the current control circuit includes a transistor, an operational amplifier and a switch module. The transistor has a gate, a first electrode and a second electrode, where the first electrode is coupled to a lighting element, and the second electrode is coupled to a resistor. The operational amplifier has positive and negative input terminals, and positive and negative output terminals. The switch module switches a connection relationship between the positive input terminal, the negative input terminal, the reference voltage and the second electrode of the transistor, and switches a connection relationship between the positive output terminal, the negative output terminal and the gate of the transistor to make the close loop form a negative feedback, and the current of the lighting element not influenced by an offset voltage of the operational amplifier.