In-field operating conditions of an integrated circuit can vary significantly. Both manufacturing (process corners and mismatch) and non-manufacturing (temperature , voltage , ageing , etc.) induced factors can influence the operation of a circuit. Especially when operating in the near-threshold region, circuits are highly susceptible to these variations. Chapter 4 clearly demonstrated this: while the measured prototypes show ultra-low energy consumption at MHz-speed performance, measuring multiple dice at multiple temperatures shows variations in the achieved results. Moreover, the simulation results showed a large span in frequency and power consumption under process variations.