A backlight unit includes light source units which emit light, and light source driving integrated circuits which control a brightness of the light source units, respectively. Each of the light source driving integrated circuits includes a current generator which generates a first current and a second current, a current level controller which controls a current value of the first current in response to duty ratio information of a pulse width modulation signal, a voltage supply unit which outputs a voltage corresponding to the second current, an output buffer unit which outputs the voltage from the voltage supply unit, and a driving switch unit which drives the light source units to allow a current corresponding to the voltage provided from the output buffer unit to flow through the light source units, where current values of the second current and the first current are the same as each other.