Knowledge Center
Knowledge Center

Dennard’s Law

An observation that as features shrink, so does power consumption.


Dennard’s Law states that as the dimensions of a device go down, so does power consumption. While this held, smaller transistors ran faster, used less power, and cost less. But there was a limit to how long this would last.

Smaller devices with thinner dielectrics and shorter channels are more prone to leakage. Leakage, while negligible for much of the industry’s history and ignored in Dennard’s original paper, now approaches the same order of magnitude as the circuit’s dynamic power. Advances such as the introduction of high dielectric constant gate dielectric materials helped, but leakage-limited transistor structures are now a fact of life. Switching a transistor at a lower threshold voltage requires a thinner gate dielectric, but leakage constraints place a lower bound on dielectric thickness. As a result, while feature sizes have continued to shrink, threshold voltage has not.

Robert H. Dennard introduced the idea in 1974 while working as an IBM researcher. It said that MOSFETs will continue to work as voltage-controlled switches in conjunction with shrinking features, providing doping levels, the chip’s geometry and voltages are scaled along with those size reductions.


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