A/d converter device and signal processing unit

An A/D converter device comprising:

• an A/D converter circuit;
• a residual voltage generator circuit operable to generate a residual voltage by amplifying a difference voltage of an input voltage and a predetermined analog voltage;
• an input switching circuit operable to input one of an external signal voltage and a voltage outputted by the residual voltage generator circuit, to the A/D converter circuit and the residual voltage generator circuit;
• and
• a control circuit operable to control execution of an A/D conversion operation and a D/A conversion operation,
• wherein the A/D conversion operation includes A/D conversion, which sets an analog voltage in the residual voltage generator circuit as a D/A conversion value of a digital conversion value outputted from the A/D converter circuit, and circulates the external signal voltage through the input switching circuit, the A/D converter circuit and the residual voltage generator circuit, and
• wherein the D/A conversion operation includes D/A conversion, which sets an analog voltage in the residual voltage generator circuit as a voltage corresponding to a binary code value supplied from an external side, circulates the analog voltage outputted from the residual voltage generator circuit through the input switching circuit and the residual voltage generator circuit, and outputs from the residual voltage generator circuit the analog voltage corresponding to the binary code value.