A 0.18-μm 10-GHz CMOS ring oscillator for optical transceivers

This paper presents a three-stage 1.8-V 10-GHz ring oscillator, implemented using the 0.18-μm digital CMOS technology. The circuit utilizes the feedforward technique at the delay cells and positive feedback provided by a cross-coupled nMOS pair in each delay cell to boost the operation speed of the oscillator. The output frequency ranges from 10.1 to 8.4 GHz with control voltages of 0 to 1.5 V. The simulated result of the phase noise is -99.9 dBc/Hz at 1-MHz offset from the center frequency of 9.2 GHz. The circuit draws 35 mA and 22 mA from the 1.8-V supply when running at the highest and lowest frequencies, respectively.