A method of driving an organic light-emitting diode (OLED) display device can include, during an initialization period, supplying a reference voltage (Vref), via a first amplifier, to a gate electrode of a driving thin film transistor (TFT) connected to an OLED element and charging an initialization voltage in a source electrode of the driving TFT; during a sensing period, supplying the reference voltage (Vref), via the first amplifier, to the gate electrode of the driving TFT, and charging the source electrode of the driving TFT from the initialization voltage to a reference sensing voltage based on the reference voltage (Vref) minus a threshold voltage (Vth) of the driving TFT; and during a sampling period, supplying a data voltage (Vdata), via the first amplifier, to the gate electrode of the driving TFT, sensing the reference sensing voltage, via a third amplifier, and supplying the reference sensing voltage, via a second amplifier, to the source electrode of the driving TFT.