PURPOSE: To improve the accuracy of D/A conversion without so much increase in the entire area by widening the area of through-holes at the end of a resistance layer and leaving the area of the through-hole at the middle as it is.

CONSTITUTION: A through-hole N5' of the same size as that of a through-hole N5 at the end of the resistance layer 1 is added to the outside of the through- hole N5 so as to bring both through-holes N5, N5' in contact with each other. Then, the parasitic resistance RN5 of this part is reduced to nearly a half in a simple consideration (in terms of the area). The reason why the N5' is provided at the outside of the N5 is that it is not necessary to change the method setting the value of the resistor R4 depending on the interval between the through-holes N4 and N5. Since the area of the through-holes of the end of the resistance layer is widened and the area of the through-hole at the middle is kept unchanged, the accuracy of D/A conversion is improved without giving so much increase in the entire area.