A digital-to-analog convertor for a driving module of a display device is disclosed. The digital-to-analog convertor includes a plurality of switches, forming a tree structure with a plurality of stages for outputting one of a plurality of gamma voltages to an output end according to a plurality of bits of a digital input signal; and a bypass unit, coupled between a first output end of a first switch in the plurality of switches and the output end for adjusting a connection between the first output end and the output end according to a most significant bit in among the plurality of bits and the bits between the most significant bit and a first bit controlling the first switch in among the plurality of bits.