A high-linearity LC-VCO with combined MOS varactors and bulk-biased PMOS varactors for gain variation compensation

A high-linearity LC-voltage-controlled oscillator (LC-VCO) with combined metal-oxide semiconductor varactors and bulk-biased P-channel metal-oxide semiconductor varactors in parallel is proposed to reduce the VCO-gain (K_VCO) variation and extend the linear range of the control voltage. Fabricated in a 180-nm complementary metal-oxide semiconductor process, the proposed topology achieves a low gain variation of less than 6.3% and a tuning range of ~28% operating from 2.31 to 3.06 GHz, corresponding to a linear control voltage range from 0.6 to 1.4 V. The phase noise is measured to be −115.3 dBc/Hz at 1 MHz offset at 3.06 GHz and the figure of merit (FoM) is −181.2 dBc/Hz. The oscillator occupies an area of 0.93 × 0.54 mm and consumes 1.8 mW from mixed 1.2/1.8 V supply voltage.