Circuit in which output circuit and operational amplifier equipped input circuit are electrically isolated

Claim 1

A function generator having a circuit input terminal and a circuit output terminal comprising: a plurality of operational amplifiers, each having a first input terminal, a second input terminal, and an output terminal; a reference voltage generating circuit for applying different reference voltages to said first input terminals of said plurality of amplifiers, individually; a resistor connected between said second input terminal of each of said plurality of operational amplifiers and said circuit input terminal to which an input voltage is applied; an electrophoto-converting element connected between said output terminal and said second input terminal of each of said plurality of amplifiers; an output circut having a plurality of photoelectric-converting elements, optically coupled with said electrophoto-converting elements, which operate when the corresponding electrophoto-converting elements operate to form a current path between a power source for said output circuit and said circuit output terminal; and a load element for converting the output current of said plurality pf photoelectric-converting elements into voltage.