Analysis of steady-state common-mode response in differential LC-VCOs

This paper analyzes the common-mode response of LC voltage-controlled oscillators (VCOs) in DC and periodic steady state regimes. The dependence of the common-mode voltage (v
_cm
) on the oscillation amplitude is theoretically studied. Closed and simple expressions for v
_cm
suitable for the VCO design and optimization are derived. The agreement with transistor level simulations has been verified in a 1.2V low-power 90nm CMOS case of study.