A current generating circuit includes a reference voltage generating unit, a clock signal generating unit, a reference current generating unit, and a current mirror unit. The reference voltage generating unit generates a first reference voltage and a second reference voltage. The clock signal generating unit generates clock signals. The reference current generating unit generates a reference current corresponding to a selection signal based on the first reference voltage. The current mirror unit supplies a first current and a second current based on the reference current. A capacitor charges voltage based on the second current. A selection signal generating unit counts clock signals during a period in which a voltage charged in the capacitor is less than the second reference voltage, and outputs the selection signal based on the counted result.