Digital-to-analog converter and method thereof

The invention relates to a digital simulation converter which generates corresponding voltage by responding to gray grade values, comprising a decoding device and an operational amplifier. The decoding device comprises a first decoding unit and a second decoding unit. By responding to the first group values of the gray grade values, the first decoding unit regards a first group voltage as a first voltage and a second voltage. By responding to the maximum value and the minimum value of the second group values of the gray grade values, the second decoding unit respectively regards a first boundary voltage as the first and the second voltages, and a second boundary voltage as the first and the second voltages. By responding to the interval values of the second group values, the second decoding unit regards the first and the second boundary voltages as the first and the second voltages. The operational amplifier can generate pixel voltage according to the first and the second voltages, the level of which lies bet