A dual-path three-stage VCO with wide tuning range

In this paper, a full integrated high-speed ring VCO is designed. The VCO consists of three stages, each of which is composed of a fast path and a slow path while the outputs of both paths are summed. Since the 0.25um CMOS technology and 3.3v voltage supply, the VCO has a wide operating frequency ranging from 800MHz to 2.1GHz with a high gain of 1.08GHz/V. PLL and frequency synthesizer will be the potential applications.