Phase-locked loop (PLL) is a circuit architecture that causes a particular system to track with another one. More precisely, PLL synchronizes a signal with a reference or an input signal in frequency as well as in phase. Phase locking is a useful technique that can provide effective synchronization solutions in many data transmission systems such as optical communications, telecommunications, disk drive systems, and local networks, in which data are transmitted in baseband or passband. The cost of electronic interfaces in communication systems raises as the data rate gets higher. Hence, high-speed circuits are the critical issue of the high data rate systems implementation, and the advanced very large scale integration technology plays an important role in cost reduction for the high-speed communication systems. PLL has an important feature, which is the ability to suppress both the noises superimposed on the input signal and generated by the voltage-controlled oscillator.