Low power wide tuning range differential ring VCO designs with I-MOS and A-MOS varactor

This manuscript reports two new designs of dual delay cells based on inversion mode MOS (I-MOS) and accumulation mode MOS (A-MOS) varactor for low power and wide tuning range differential ring voltage controlled oscillator (VCO). The new designs obtained a large tuning range by varying the capacitance of the delay stages. The change in capacitance across I-MOS and A-MOS varactor are obtained by varying the gate control voltage (Vg). The proposed VCO circuits are simulated in 0.18 µm CMOS process with a supply voltage (Vdd) of 1.8 V. The tuning ranges of VCO-I (with I-MOS varactor) and VCO-II (based on A-MOS varactor) vary from 1.697–0.714 GHz (81.54%) and 2.019–0.874 GHz (79.15%), whereas their power consumption vary from 4.347–3.507 mW and 3.713–3.063 mW respectively, by modulation of control voltage (Vc) from 0 V to 1 V. The phase noise of ring VCO-I and VCO-II is −103.1 dBc/Hz and −101.2 dBc/Hz at 1 MHz offset from 1.270 GHz and 1.516 GHz central frequency respectively. The figure of merit (FoM) of the VCO-I and VCO-II is −158.92 dBc/Hz and −159.32 dBc/Hz respectively and acquires an area of 0.381 mm2.