A 330 µW, Gm-boosted VCO with −205 dB FoMT and 35 % tuning range using class-b biasing

In this paper, we present an ultra-low power VCO with a supply voltage of 0.5 V. The proposed VCO uses class-B biasing with optimum switching amplitude for the tail current sources to improve the phase noise. Using a G_m-boosted structure, the parasitics at the LC-tank have been reduced, thus resulting in a larger tuning range. Using the proposed technique, a phase noise improvement of 2.8 dB at 50 KHz offset and 2.2 dB at 1 MHz offset were achieved. The proposed design was implemented in a 65 nm CMOS process. The VCO achieves a tuning range of > 1 GHz with nominal power consumption of 330 μW, the lowest among VCOs with comparable performance. The proposed VCO achieves an excellent figure-of-merit with a tuning range (FoM_T) of -205.4 dBc/Hz at 2.41 GHz.