Fundamental limits to power consumption of LC subthreshold oscillators

The performance of different LC oscillator topologies is evaluated, showing that their current and power requirements are fundamentally equivalent for many commonly employed single-stage circuits, and are subject to a practical lower limit dictated by the characteristics of the active devices and inductors used. Two fundamental quality indi- cators are defined, which can summarise their current and energy per- formance. An example of a two-stage circuit is provided, which is not subject to that limit.