In this paper, a voltage-controlled ring oscillator (VCO) with wide linear tuning frequency range capability based on transmission gates is described. It also features the rapid voltage swing and the 50% duty cycle independent of the control voltage. Fabricated in TSMC 0.35µm 1P4M, 3.3V CMOS process, the VCO achieves an operating frequency range of 4.8Hz to 256MHz. The measured peak-to-peak and rms jitter are 41 and 5.8 p-sec as operating at 200 MHz.