To mitigate kickback noise effect, the present invention provides a reference voltage generator for an analog-to-digital converter circuit. The reference voltage generator includes a bias generator, a bias converter and an output unit. The bias generator is used for generating a first bias voltage in accordance with a reference voltage. The bias converter is coupled to the bias generator and is used for converting the first bias voltage to a second bias voltage. The output unit is coupled to the bias converter and used for generating a first voltage to a load circuit in accordance with the second bias voltage.