Optimum VCO´s for radiofrequency applications

This paper presents voltage controlled oscillator (VCO) circuit employing MOS transistors intended for integrated transceiver, in which full compensation of process parameters variations can be obtained. This is realized by fitting on chip capacitance of LC resonator. This capacitance is used for tuning of resonant frequency. VCO output frequency is tuned by on-chip p /n-well junction varactors. The circuit topology minimizes the amount of fixed parasitic capacitance in the tank circuit. The simulation results show that the proposed VCO can reach the frequency wished to the telecommunication application. Parameters from an industrial 0.35 mum CMOS process are used for simulations. The nominal operating frequency of these oscillators is 2.4 GHz. They are designed to be resistant to supply and temperature effects. This oscillator achieves the necessary temperature and supply independence while being tunable about 2.4 GHz. Using only 2.5V of power supply and IV of tuned voltage, the circuit shows a simulated single-output sensitivity of 565 ppm/degC at 27degC temperature and -0.47%/Volt at 2V