Voltage summing buffer, digital-to-analog converter and source driver in a display device including the same

PURPOSE: A voltage summation buffer, a digital-to-analog converter and a source driver of a display device including the same are provided to reduce the number of voltage lines for supplying voltage lines. CONSTITUTION: A digital-to-analog converter(1000) includes a first decoder(130), a second decoder(160) and a computation summation buffer. The first decoder receives upper bits or upper reference voltages of a digital signal and outputs upper voltage corresponding to the upper bits. The second decoder receives lower bits or lower reference voltages of a digital signal and outputs lower differential voltage corresponding to the lower bits. The computation summation buffer generates output voltage corresponding to the digital signal based on the upper voltage or the lower differential voltage.