System-on-a-Chip (SOC) refers to integrating all components of a computer or other electronic systems into a single integrated circuit. It may contain digital, analog, mixed-signal, and often radio-frequency functions for communications – all on one chip. SOC is believed to be more cost effective since it increases the yield of fabrication and reduces packaging efforts. Presently, the bottleneck of SOC developments is the interfaces among its sub-functional blocks since an SOC system comprises a variety of different functional blocks such as DSP, memories, microprocessors, wireless communication circuits, wired communication circuits, system timing generators, data converters, voltage regulators. Because of the integration of different fabrication-technology circuits for different functional blocks on the same chip, the circuit design of internal signal interfaces between analog and digital circuits, low-frequency logic circuits and high-frequency communication circuits can be a tough challenge especially its analog circuit design since the analog circuits for communication are more sensitive to noise interference, temperature and process variations. The analog circuit design techniques for communication SOC, which enable a larger design tolerance while maintaining the simplicity of the circuits are therefore highly desired.