A New Boosted Active-Capacitor With Negative-<i>G</i> <sub>m</sub> for Wide Tuning Range VCOs
Pawan Agarwal, Mohammad Chahardori, Deukhyoun Heo
Abstract
A new boosted active-capacitor (BAC) architecture using LC-tuned active-impedance-conversion is presented. In the chosen frequency range, the proposed BAC acts as a tunable capacitance multiplier and negative-transconductance, but where the positive-transconductance is not multiplied. The BAC is used as a low-loss tunable capacitor bank element for designing a wide tuning range voltage-controlled oscillator (VCO). A current-reuse technique is used to lower power consumption and suppress potential parasitic oscillation modes. A zero-capacitance-variation biasing is proposed for a BAC-VCO robust against process, voltage, and temperature variations. The BAC designed in a 65 nm bulk CMOS process achieves a capacitance tuning ratio of 7.8 with a quality factor of higher than 20 across VCO's tuning range. The BAC-VCO prototype has a tuning range of 8.3-14.3 GHz using less than 5 mW core power and achieves FoMT of up to -202.4 dBc/Hz.