An all-inversion-region MOST design methodology applied to a ratioless differential LC-VCO

This paper presents a general optimization methodology for analog blocks in RF applications, with CMOS nanometer technologies, based on the complete exploration of all-in- version regions of MOS transistor (MOST). The fundamental tool is the systematic use of the MOST gm/ID technique and the description of the real behavior of all devices by means of semi-empirical models. To exemplify this technique, the differential ratioless cross-coupled LC-tank voltage controlled oscillator (LC-VCO) circuit is studied. The implemented design flow minimizes the LC-VCO phase noise considering the constraints of current consumption, output common-mode voltage and output amplitude. To verify the method, six LC-VCO were designed and validated by comparing them with the corresponding electrical simulations.