Variable impedance circuit

摘要

A variable impedance circuit has an impedance block including a plurality of MOS transistors connected in parallel by switching and having impedances in accordance with powers of 2, the powers corresponding to the sequential orders of the MOS transistors arranged. A control unit controls ON or OFF of each of the MOS transistors to thereby select one of overall impedances of the MOS transistors. The step difference in the variable impedances is substantially a constant irrespective of the overall impedance selected.