A Pulse-Tail-Feedback Lc-Vco With 700 Hz Flicker Noise Corner And-195 Dbc Fom

This paper proposes a pulse-tail-feedback VCO, in which the tail transistor is driven using pulse-shaped voltage signals with rail-to-rail swing. The proposed pulse-tail-feedback (PTFB) VCO relies on reducing the current conduction period of the tail transistor and operating the tail transistors in triode region for reducing the flicker and thermal noise from the active elements. Mathematical analysis and circuit level simulations of the phase noise mechanism in the proposed PTFB-VCO is also presented in this paper for validating the effectiveness of the proposed technique. A prototype LC-VCO with the proposed PTFB technique is fabricated in a standard 180 nm CMOS. Laboratory measurement shows a power consumption of 1.35 mW from a 1.2V supply at 4.6 GHz. The proposed PTFB-VCO achieves a flicker corner of 700 Hz, which enables the VCO to maintain a fairly constant figure-of-merit (FoM) of -195 dB within a wide offset frequency range of 1 kHz-10 MHz.