PURPOSE: To improve the resolution of a D/A converter without increasing the bit number of the D/A converter by connecting an amplifier having plural kinds of amplification factors to the D/A converter.

CONSTITUTION: In the D/A converter circuit, a feedback resistor 10 for switching amplification factor shown in broken lines and an analog switch 11 are added to a conventional circuit to change the amplification factor into two ways as R1/2 and R1. As a result, an output of 512(0∼511) stages is obtained from a voltage output 8 of the D/A converter regardless of the use of an 8-bit D/A converter 4 and the resolution is 1/511 with respect to the full scale of the unity. Thus, an analog output with high resolution and high accuracy is obtained even with the D/A converter of the same bit and the resolution is doubled as an output width (b) with respect to an input width (a).