A Low-Voltage Low-Power Wide-Tuning-Range Hybrid Class-AB/Class-B VCO With Robust Start-Up and High-Performance ${\rm FOM}_{ T}$

This paper proposes a hybrid class-AB/class-B voltage-controlled oscillator (VCO) with low voltage, low power, and a wide tuning range. The class-AB VCO core is designed to ensure robust start-up of the class-B VCO core. Featuring a high-efficiency class-B VCO core, the combination of class-AB/class-B VCO cores consumes low dc power. Based on the proposed architecture, the fabricated 0.18-μm CMOS VCO exhibits a measured tuning range of 25.6%. Operating at a low supply voltage of 0.75 V, the hybrid class-AB/class-B VCO cores consume a low total dc power of 2.4 mW. In this bias condition, the measured average value of phase noise for all frequency ranges is -101.4 dBc/Hz at 1-MHz offset from the carriers. Compared to recently published wide-tuning range VCOs, the proposed hybrid class-AB/class-B VCO simultaneously achieves a low supply voltage, a low dc power dissipation, and wide tuning range, leading to a good figure-of-merit including the tuning range (FOM_T). In addition, the theories for analyzing the VCO are given in detail, and the mechanisms are validated by experiments.