Design of CMOS Based VCO for PLL with Improved Frequency Range
A Voltage Controlled Oscillator (VCO) is one of the most important basic building blocks in analog and digital circuits. There are many different implementations of VCOs. One of them is a ring oscillator based VCO, which is commonly used in the clock generation subsystem. The proposed VCO circuit is designed to achieve frequency greater than 2GHz using TSMC 0.18 micron CMOS technology and simulated with Mircrowind. In proposed VCO two topologies have been used, one is by using inverter and other is by using differential amplifier. The inverter topology uses odd number of inverters and it provides small circuitry, low complexity and problems in developing oscillations.