Design Of A Voltage controlled Ring Oscillator Based On MOS Capacitance
With the wireless communication industry developing rapidly, CMOS circuits which are low-cost, low-power, high stability become the best wireless communication system solutions. In the communication system, the voltage controlled oscillator (VCO) is the important component, especially in the PLL circuit, clock recovery circuit and frequency integrated circuit, so it is the top priorities. According to oscillator principle, oscillator can be divided into two categories: One is the LC oscillation which is composed of the active devices, coupled with LC resonant circuit. Another one is the loop ring oscillator which is composed of delayed cascade units with a positive feedback. In this paper the design using TSMC 0.18μm CMOS process, completed in the Cadence design environment The traditional ring voltage-controlled oscillator (VCO) generally uses the method of controlling resistance to change the oscillation frequency. This paper describes a 2GHz fully differential ring voltage-controlled oscillator based on 0.18μm CMOS technology. The oscillation frequency is controlled through MOS capacitance in the output of each delay cell. This method has stabile output waveform and linear tuning characteristic.