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This paper presents a low phase noise fully integrated CMOS LC voltage-controlled oscillator (VCO) for 5-GHz WLAN applications. Low phase noise has been achieved by the use of the pMOS current source with a large gate length and bias filtering. The tail current source as well as the mirror has been kept large so that flicker-noise upconversion is minimized without degrading thermal noise. Bias filters are used in VCO to suppress reference current noise and dynamic transient effects on the bias line. The VCO is designed and implemented to evaluate the concept using 0.18-mum TSMC CMOS process. The VCO has a tuning range of 264 MHz and phase noise of -116 dBc/Hz at 1 MHz offset frequency at the 5.32-GHz carrier. The figure-of-merit (FOM) of the VCO is -183.1. This VCO consumes 3.17 mA from a 1.8 V supply.