A driving unit for a LCD device, including: a ramp signal generating unit for dividing a ramp signal into a first ramp signal and a second ramp signal; an input register unit for sequentially storing N-bit image data; a counter unit for outputting control signals by receiving bits of image data except for the most significant bit and counting based upon the received bits; a ramp signal selecting unit for selecting the first ramp signal or the second ramp signal according to the most significant bit and outputting the selected ramp signal upon receiving the most significant bit from the input register unit; and a switching unit for sampling the first ramp signal or the second ramp signal provided from the ramp signal selecting unit by the control signals of the counter unit and outputting the sampled ramp signal to data lines.