The need for low-power, area efficient, high speed VCO is pushing toward the use of dynamic regenerative oscillators to maximize speed and power efficiency. In this paper, an analysis on the fast frequency of the dynamic VCO will be presented and analytical expressions are derived. From the analytical expressions, designers can obtain an intuition about the main contributors to the vco, delay and fully explore the tradeoffs in dynamic vco design. Based on the presented analysis, a new dynamic VCO is presented by using dynamic double tail comparator. The entire design flow has been done by using Tanner EDA Tool in 180 nano meter technology.