Oscillator Case Study

Study and Design of Current Starved Voltage Controlled Oscillator using Ring Oscillator @ 45nm CMOS Technology
Sharad kumar1, Soumendra Kumar Dash2, Sidhant Sahoo3, Bandi Jagdeeshwar Reddy4,
Suraj Kumar Saw5, Deepak Prasad6, Vijay Nath7
Department of ECE VLSI Design Group
Birla Institute of Technology, Mesra, Ranchi, India
Email: [e-mail]

Abstract-The implementation of CMOS technology in communication field has become the need in present scenario so as to develop such devices which are compact, noise free and dissipate ultra low power. An oscillator is used in order to generate a periodic signal or waveform for various applications. These applications vary from clock generation in microprocessors to carrier synthesis in cellular phones. All these applications require different types of oscillators that can be connected in various topologies. There are many circuit techniques that are used to develop a VCO. In this paper7 stage Current Starved voltage controlled oscillator (CSVCO) circuits are designed using gpdk45nm CMOS technology. Now CMOS technology is superior in VLSI than others in the view of low power

Introduction
A voltage controlled oscillator (VCO) has various applications in communication systems. It is used in direct generation method of FM while in demodulation it is used in PLL method. Though other demodulation methods are also used like balanced slope detector, foster-seeley detector, ratio detector and slope detector but only PLL method has been described here because except the PLL method all other techniques require additional transformers [1].
The input of VCO is m(t) which is taken as feedback from output of a low pass filter as shown in the Figure1. The frequency of VCO output will be varied w.r.t. m(t) so that frequency synchronization will be maintained with FM