On amplitude and operating point control of a voltage-controlled crystal oscillator

In this work, a system architecture is presented for a voltage-controlled crystal oscillator (VCXO) with integrated Pierce structure and varactors in a deep submicron CMOS process. To meet low crystal drive, wide pull range, and negative resistance specifications in a low power supply leads to Pierce VCXO designs requiring both amplitude and operating point regulation. In this design, an automatic amplitude control (AAC) loop and embedded replica bias are implemented with the Pierce cell to provide the required regulation.