A light-emitting diode (LED) driver, an LED lighting apparatus, and a method of operating the LED lighting apparatus are provided. The LED driver may include an LED current controller configured to control an LED current, which flows through an LED array including a plurality of LEDs, such that the LED current is maintained at a constant level; a comparer configured to compare a sensing signal, which corresponds to a magnitude of the LED current, and a reference signal, and to obtain a first output signal based on a comparison result; and a dimming controller configured to modify the first output signal to obtain a second output signal for dimming of the plurality of LEDs, and to provide the second output signal to the LED current controller.