Abstract— Tuning Range of Oscillator is one of the important specification which is used in phase locked loop. The more wider tuning range, the better the phase lock loop. This paper proposed regulated cascode cross coupled based CMOS oscillator. The analysis and simulation results of tuning range of this type of oscillator are compared with conventional Colpitts based CMOS oscillator as a function of bias current consumption. Index Terms— Tuning Range, CMOS oscillators, Regulated Cascode cross coupled VCO I. INTRODUCTION The conventional method of analysis and design of Colpitts based CMOS Oscillator is not following Barkhausen criterion [1]. By substituting low frequency small signal equivalent circuit of CMOS into single ended Colpitts based CMOS oscillator and injecting input current source into the circuit, we can derive the transimpedance gain of the circuit. Then, we can equate the real part and imaginary part of the function to zero. After that, we can obtain two equations of oscillating frequency as a function of passive components. Then, if we equate both of the equations, substitute the capacitance ratio. We can derive minimum required gain for the Colpitts based circuits. In contrast to the single ended Colpitts based CMOS oscillator. The cross coupled differential Colpitts based CMOS oscillator can not be designed by the same way as single ended Colpitts based CMOS oscillator but it follows Barkhausen criterion [2]. It is different because cross couple differential Colpitts based CMOS oscillator can be seen as a 2 stage amplifier in cascade while output of the second stage amplifier is fed back into input of the first stage amplifier Section II describes how to design tuning range of single ended Colpitts based CMOS oscillator by switching the bias resistor. Section III describes how to design tuning range of cross coupled differential Colpitts based CMOS oscillator. Section IV describes how to design cross coupled differential Regulated Cascode based CMOS oscillator. Manuscript received March 12, 2013 Kittipong Tripetch, Division of Electronic and Telecommunication Engineering, Faculty of Engineering and Architecture, Rajamangala University of Technology Suvarnabhumi, Nonthaburi Campus 7/1 Nonthaburi1 Road, Suan-Yai, Muang, Nonthaburi Province, Thailand, 11000, k3101600678282@windowslive.com II. ANALYSIS AND SIMULATION OF SINGLE ENDED COLPITTS BASED CMOS OSCILLATOR The conventional Colpitts based CMOS oscillator was designed in [1]. It was given by       㻞㻟㻞㻟㻞㻝㻟㻝㻞㻞㻝㻞㻝㻝㻞PP㼙㼛㼡㼠㼕㼚㼛PPP㼙PP㼛㼙P㻾㻸㼟g㻯㼟㼂㻵㼍㼟㼍㼟㼍㼟㼍㼍㻾㻯㻯㻸㼍㻯㻯㻸㼍g㻾㻾㻯㻯㼍g㻾              (1) where 㻞㻞㻰㼙㼚㼛㼤㻰㻳㻿T㻴㻵㼃g㻯㻵㻸㼂㼂     is small signal transconductance of the MOS transistor. 㻰㻰㼂P㻸P㻾㻞㻯㼛㼡㼠㼂㼎㻵㻝㻹㻝㻯㻝㼂㻝㼙g㼂㼕㼚㻵㻞㻯㻝㻯P㻸P㻾㼛㼡㼠㼂   㼍  㼎㼎㼂 Fig. 1 (a) Single ended Colpitts based CMOS oscillator (b) Small signal equivalent circuit of (a) Comparative Analysis of Tuning Range of Regulated Cascode Cross Coupled CMOS Oscillators Kittipong Tripetch Proceedings of the World Congress on Engineering 2013 Vol II, WCE 2013, July 3 - 5, 2013, London, U.K. ISBN: 978-988-19252-8-2 ISSN: 2078-0958 (Print); ISSN: 2078-0966 (Online) WCE 2013