Abstract: In this paper, CMOS digitally controlled oscillator (DCO) design is analyzed for 4-16 bits. The CMOS DCO is designed based on a ring oscillator. Simulations of the analyzed DCO using 250nm CMOS technology achieve controllable different frequency range with a wide linearity. A 4-bit digitally controlled CMOS oscillator (DCO) design is best by adjusting the width of p-MOS and n-MOS devi...