A low-voltage high-swing colpitts VCO with Inherent tapped capacitors based dynamic body bias technique
A low-voltage high-swing voltage-biased Colpitts voltage-controlled oscillator (VCO) is proposed for wireless applications. A small capacitive voltage divide factor is chosen to enhance the output swing and improve the phase noise performance. To further enhance the negative resistance, and thus decrease the start-up time, the bulk terminals of the gm-boosting transistors are dynamic-biased by the low-swing nodes provided by the inherent tapped capacitors in Colpitts VCOs. Due to the switching operation mode of the gm-boosting transistors and the absence of common-mode nodes for the switching transistors, the flicker noises up-conversion is largely suppressed. Designed in a 0.18-μm CMOS process, the postlayout simulation results show that it provides a phase noise of −127.66 dBc/Hz at 1 MHz offset centered at 3.76 GHz and a figure-of-merit (FoM) of 192.4 dBc/Hz while dissipating 4.71 mW from a 0.6 V supply. The tuning range is 17% (from 3.28 GHz to 3.89 GHz) and the 1/f 3 phase noise corner is only 60 kHz.