Design of a 2.4-GHz MEMS-Based Oscillator With Dynamic Self-Body-Biasing Scheme and Darlington Cell

In this article, a 2.4-GHz micro-electromechanical systems (MEMS)-based oscillator is designed and demonstrated based on
$g_{\text {m}}$
-boosting Colpitts structure. A dynamic self-body-biasing scheme is proposed to shorten startup time without introducing any extra units or additional parasitics to the resonant tank. Darlington cell is also employed to enhance negative transconductance and improve the oscillation stability, especially under a low supply voltage operating condition. The oscillator is integrated with a 2.4-GHz MEMS resonator with high
$Q$
characteristic. The tail current source is designed at the boundary of the current- and voltage-limited regime for a superior phase noise performance. The measurement result shows that the phase noise at 10- and 100-kHz offsets is −112.92 and −138.23 dBc/Hz, respectively. A figure-of-merit of 226 dBc/Hz is achieved. The measured startup time is
$\sim 5 \mu \text{s}$
. The core oscillator consumes a dc power of 0.98 mW from a 0.7-V supply voltage.