Differential pair refers to a pair of coupling transmission lines. The transmission of differential signal is the process in which two output drivers drive differential pair one of which features signals while the other features its complementary signal. Voltage difference between differential pairs is the most required, with information for transmission. Signals transmitted by two terminals on differential transmitter have the same size and contrary phase positions. If two signals arrive at the receiving terminal simultaneously, signals will receive correct reception. However, delay will possibly take place in the process of transmission and if the transmission distance of the signal from one terminal is relatively long, the delay will rise so that relative relay will take place between two signals, which means a phase placement of a signal. Under such circumstance, distortion will take place to differential signal at the receiving terminal. If the magnitude of distortion becomes too big, problems will take place such as abnormal signal receiving at the receiving terminal and the function of circuit fails to come true. Therefore, relative delay between two differential signals should be minimized.