Tail current flicker noise reduction in LC VCOs by complementary switched biasing

Abstract

A new LC voltage-controlled oscillator circuit topology is proposed, in which the flicker noise generated by the tail transistor is noticeably reduced by utilizing the phenomenon of flicker noise intrinsic reduction due to switched biasing. A macro model of MOSFET under switched biasing is used to prove the idea. Circuit simulations are done on two oscillators with the same tail current value; one with fixed biasing and the other with the proposed switching. A 4 dBc/Hz phase noise improvement is achieved at 1 kHz frequency offset in the switched biasing scheme under the same power dissipation and tuning range.