US Patent 10897253 Calibration circuit and calibration apparatus including the same

A system may include: a first memory device; a second memory device; a third memory device; and a fourth memory device, wherein the first memory device to the fourth memory device are configured to share a resistor for impedance matching, wherein the first memory device to the fourth memory device are coupled to have a chain shape, wherein the forth memory device generates a completion signal when performance is completed and the first memory device receives the completion signal provided from the fourth memory device.