PURPOSE: To provide the digital converting ability of high accuracy, regardless of a small chip area, by providing a voltage generating circuit, the 1st and 2nd switch circuits, a control circuit and a comparison circuit.

CONSTITUTION: A voltage divided with resistors is generated, by applying a constant voltage to a voltage generating circuit 10 having a series circuit consisting of resistors R0∼R7, and this voltage is applied to a switch circuit 14. The circuit 14 selects one of output of the circuit 14 in response to A4∼A2-bit of the high-order group of digital data A4∼A0 being an output of a control circuit 32 and applied to a transistor TR2 as an output VR1. Further, a part of the circuit 10 is applied to a switch circuit 16, which selects one of outputs of the circuit 10 according to low-order groups A1, A0 of an output of the circuit 32 to form an output VR2. An analog voltage VIN and a voltage of the output VR1 are compare 30 and the result X of comparison is outputted to the circuit 32. The circuit 32 generates new digital data A4∼A0 based on the result X.