Study of CMOS voltage controlled oscillator design

In the design of phase lock loop (PLL), the voltage controlled oscillator is a most important component, and the well design of it determines the performance of the whole circuit. By reading the PLL papers of resent years, we first make an introduction and analysis about the operating principle and characteristics of the VCOs. Then, we introduce the varied architectures of the VCOs, classify them according to the structure, and compare them by analyzing the characteristics in-depth.