What is leakage current and why do I care?

I frequently hear semiconductor companies proclaiming the low leakage of their transistors.

But what do they mean and why should we care?

Many expressions describe transistor leakage; leakage, off current, standby current, sleep current, IOFF and many more. The terminology is confusing and perplexing.

These expressions describe one aspect of the transistor, the amount of current that flows through the transistor when it is off. A transistor is a switch that has two states either off or on. 0 or 1.

In the world of transistor physics, the leakage current for a FinFET is

A modern microprocessor such as Apple’s A12X Bionic, manufactured by TSMC using their 7nm FinFET process, has 10,000,000,000, (ten billion), transistors. Consider what the battery life of your laptop, phone or tablet would be if these transistors have a high leakage current; if current flows and energy is consumed when the transistor is in its off state.

High transistor leakage = unnecessary power consumption=lower battery life

Semiconductor manufacturing companies assert their leakage prowess because lower leakage translates to longer battery life for the mobile user.

For server farms, the transistor leakage is critical too. In a server farm, one of the few variable costs is power consumption, the electricity bill. For the sake of profits and the planet, server farms need integrated circuits with low leakage transistors. High transistor leakage also leads to high extra cooling costs for the server farms. (J. W. Tschanz, S. G. Narendra et al. 2003)

A portion of the total power consumption in high performance integrated circuits is due to leakage currents, the current that flows through transistors that are in an off state. (J. W. Tschanz, S. G. Narendra et al. 2003)

So the next time your laptop battery starts to near 0%, think- leakage current.

References

J. W. TSCHANZ, S. G. NARENDRA, Y. YE, B. A. BLOECHEL, S. BORKAR and V. DE, 2003. Dynamic sleep transistor and body bias for active leakage power control of microprocessors.

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