A 3.6-mW 6-GHz current-reuse VCO-buffer with improved load drivability in 65-nm CMOS

A new current-reuse voltage-controlled oscillator (VCO)-buffer with enhanced load drivability is proposed. It incorporates a PMOS-based source follower stacked atop a NMOS-based LC VCO to share the bias current, while preventing the voltage stress at any oscillation node from exceeding the 1.2-V technology voltage limit. Also, ac-coupling networks are avoided between the VCO and buffer, improving the Q of the LC tank while minimizing parasitics. With internal buffering, the VCO can directly drive up a 50-Omega load for testing, or to withstand a large capacitive load in on-chip local oscillator distribution, particularly suitable for multi-band MIMO WLAN radios. The fabricated VCO-buffer in 65-nm CMOS measures 13.8% tuning range from 5.64 to 6.4 GHz, consumes 3.6 mW at 1.2 V and exhibits -108.84 dBc/Hz phase noise at 1-MHz offset. Copyright (c) 2013 John Wiley & Sons, Ltd.