Patent ID: 7317336

Claim:
An input-output circuit comprising: a driver which transmits a predetermined signal to a semiconductor integrated circuit; a comparator which receives an output signal from the semiconductor integrated circuit; a transmission line which is connected between the driver and/or the comparator and the semiconductor integrated circuit and transmits the predetermined signal and/or the output signal; and an impedance matching circuit provided between the transmission line and the semiconductor integrated circuit to receive the output signal from the semiconductor integrated circuit and to output the received output signal with low impedance; wherein the impedance matching circuit is comprised of: a first resistance; a first analog computing unit which multiplies a voltage at one end of the first resistance by a predetermined number, subtracts a voltage at the other end of the first resistance from the voltage multiplied by the predetermined number, and outputs a voltage obtained by the subtraction; a second resistance connected to an output side of the first analog computing unit; and a second analog computing unit which multiplies a voltage at one end of the second resistance by a predetermined number, subtracts a voltage at the other end of the second resistance from the voltage multiplied by the predetermined number, and outputs a voltage obtained by the subtraction, wherein the first resistance is connected to an output side of the second analog computing unit.