VLSI circuits in nanometer VLSI technology experience significant aging effects, which are embodied by performance degradation over operation time. Although this degradation can be compensated by over-design, it induces remarkable power overhead which is undesirable in tightly power-constrained designs. Dynamic voltage scaling (DVS) is a more power-efficient approach. However, its coarse granularity implies difficulty in handling fine-grained variations in the aging effects. We propose a Built-In Proactive Tuning (BIPT) system that allows each circuit block to autonomously tune its performance according to its own degree of aging. The BIPT system is validated through SPICE simulations on benchmark circuits with consideration of NBTI effect. The experimental results indicate that the proposed BIPT system leads to about 45% less power than the approach of over-design while maintaining the same performance. Compared to DVS, BIPT can achieve the same aging resilience with about 30% less p...