Abstract: A method and apparatus for converting digital input signal to analog voltage are disclosed herein. The converting apparatus includes the following devices device. One of the pair of reference voltage selecting means is used to select a first voltage level as a first power source. Similarly, a second voltage level is selected as a second power source. The pair of controlled selectively coupling devices couples the first power source or the second power source as the charge power source responding to voltage level of every bit of the second portion of the digital input signal. The voltage cumulating device is used to generate the analog voltage by alternatively charging and redistributing the output capacitor with the first and the second capacitor. The foregoing method includes the following steps. At first, divide reference voltage levels into a first set and a second set of reference voltage levels.