Semiconductor Integrated Circuit

A transmission system, comprising:

• a transmission line;
• a terminating resistor to be impedance-matched to said transmission line;
• and
• a semiconductor integrated circuit for matching the resistance of a variable resistor, which is used as a terminating resistor or a reference of said terminating resistor, to the characteristic impedance of a transmission line, comprising a terminating resistor adjusting circuit that has a current circuit connected to a power supply, said variable resistor that is connected between said current circuit and the ground and receives a main current output from said current circuit, a comparator circuit that compares the potential of the variable resistor with a first reference potential and outputs a signal, and a control circuit that controls the resistance of said variable resistor based on the output signal of said comparator circuit;
• and an additional current adjusting circuit that is connected between said power supply and said variable resistor and outputs an additional current to said variable resistor according to an external signal determined by the resistance of an external parasitic resistor between said terminating resistor and said transmission line.