A 400 μW Near-Threshold Feedback Class-C VCO with Auto Amplitude Control

Abstract

A 400[Formula: see text][Formula: see text]W near-threshold supply class-C voltage controlled oscillator (VCO) with amplitude feedback loop and auto amplitude control (AAC) is proposed in this paper. The amplitude feedback loop and AAC ensure the robust startup of the proposed VCO and automatically adapts it to the class-C mode in steady state. Consequently, ultra-low power can be achieved in AAC mode and low phase noise, high swing can be achieved in AAC off mode. The proposed VCO with AAC gets ultra-low power consumption by limiting the oscillating amplitude and driving the proposed VCO into the deep Class-C mode. Additionally, the peak value detector is employed in this work to boost the controlling voltage of capacitors bank. Thus, a low on resistance of switch transistors is obtained, which increases the Q value of capacitors bank. The simulated phase noise is [Formula: see text]124.5[Formula: see text]dBc/Hz at 1[Formula: see text]MHz offset with the 1.16[Formula: see text]GHz oscillation frequency. In this case, the figure-of-merit including tuning range (FOMT) of proposed VCO is [Formula: see text]195[Formula: see text]dBc/Hz. The proposed VCO is fabricated in SMIC 40[Formula: see text]nm CMOS process and consumes 0.62[Formula: see text]mA from 0.65[Formula: see text]V supply. The measured phase noise is [Formula: see text]109[Formula: see text]dBc/Hz and FOMT is [Formula: see text]179[Formula: see text]dBc/Hz.