The present invention discloses a digital-to-analog converter (DAC), including a bias voltage generating unit, a digital-to-analog converting stage, and an operating amplifier. The bias voltage generating unit is utilized for generating a first bias voltage. The digital-to-analog converting stage is utilized for converting a digital signal into a voltage signal, the digital-to-analog converting stage includes a current source for providing a current, and a switching unit is coupled to the current source for controlling the current to pass the switching unit according to the digital signal, and a load. The current flows through the load to generate the voltage signal. The operating amplifier is coupled to the bias voltage generating unit and the digital-to-analog converting stage for controlling the current source according to the first bias voltage.