In a source driver output circuit of a flat panel display device, first and second latch units receive image data and store the received image data. A D/A converter converts the image data into a data voltage. An output buffer unit outputs the data voltage to a data line. A switching control unit decides whether or not the data voltages of two image data of the same channel among image data of horizontal lines adjacent to each other, stored in the first and second latch units, belong to the same grayscale voltage range, and outputs a switching control signal based on the decided result. A multiplexer unit selects a pre-charge voltage in response to the switching control signal or continuously maintains a connection state between a corresponding channel of the output buffer unit and the corresponding data line.