There is provided an integrated circuit which performs data input/output operations through a transmission line with a predetermined impedance. The integrated circuit includes a driver having a plurality of driving units, in which the driving units input/output data from/to the transmission line, and a controller for inputting an output data signal and applying a plurality of control signals to the driver, in which the control signals are generated in response to an output activation signal and impedance code signals related to states of the impedance. At least one driving unit is driven in response to the control signals, and the driver includes an on-chip termination circuit connected to an input buffer.