A novel high-swing Class-C VCO with an amplitude feedback loop is presented. The amplitude feedback loop is used to ensure the start-up of the VCO which also makes the proposed VCO always have an optimal phase noise against the PVT variations automatically. The proposed circuit is implemented in a 65 nm CMOS process. The VCO has exhibited a measured phase noise of −128.6 dBc/Hz at 1 MHz offset from the 1.52 GHz carrier frequency with a 1.4 mW power consumption. The variation of measured phase noise at 1 MHz offset is less than 2.3% while temperature changes from −40 • C to 100 • C.