A/D CONVERTER

PURPOSE:To allow one ladder resistor to convert two analog signals in parallel by giving an output reference voltage from the ladder resistor to the other comparator when the reference voltage is not inputted to one comparator to enhance the ladder resistor utilizing efficiency. CONSTITUTION:When a switch 2A2 is closed by an H level sampling clock phiand a reference voltage VREF1 is inputted to a comparator 3A from a ladder resistor 4 in response to a value of an A/D conversion register 7A, an analog voltage ANV2 is inputted to a comparator 3B. Moreover, when a switch 2A1 is closed by an L level sampling clock of the inverse of phi and a reference voltage VREF2 is inputted to a comparator 3B. Thus, the utilizing rate of the resistor 4 is enhanced. Thus, when two analog voltages ANV1, ANV2 are ADD- converted, since the single resistor 4 is used, the pattern occupied area of the resistor 4 is reduced.