Abstract: This paper presents an improved design of voltage controlled oscillator (VCO) utilizing the three differential cell CMOS inverters for forming the ring oscillator. The differential cell reduces the power supply fluctuations impact on the oscillator jitter while the negative feedback from frequency to voltage converter reduces the jitter at high frequencies. Finally the proposed model is designed using CMOS 0.18um foundry technologyand simulated using P-Spice software. The result shows that the proposed design improves the jitter attenuation at different offset frequencies up to 40dB.