Patent ID: 7504974

Claim:
A selecting circuit comprising: a plurality of first circuit groups, each of which includes: a selecting circuit input terminal; a first resistor group composed of two or more serially connected resistors and having a first end connected to said selecting circuit input terminal; a first semiconductor switching element having a first end connected to any one node between two resistors in said first resistor group; a second semiconductor switching element having a first end connected to a second end of said first resistor group; and a third semiconductor switching element having a first end connected to the second end of said first resistor group; an operational amplifier having an inverting input terminal connected in common with second ends of said first semiconductor switching elements in respective ones of said first circuit groups, and an output terminal connected in common with second ends of the second semiconductor switching elements in respective ones of said first circuit groups; and a selecting circuit output terminal connected in common with second ends of said third semiconductor switching elements in respective ones of said first circuit groups.