A Small Negative Charge Saves 10,000 Picawatts of Transistor Power Leakage


Internet-of-Things Radio Chip Consumes a Little Power to Save a Lot

IEEE Spectrum, February 25, 2015

Connected devices, which are seemingly everywhere these days, all require power to send data wirelessly. The need of each thing on the Internet of Things might be small, but the number of devices is expected to more than double between now and 2020 to more than 30 million, according to ABI Research.

Anantha Chandrakasan, professor of electrical engineering at MIT, presented a new transmitter design that reduces power leakage when a radio is in the off state by 100-fold. Even though it has ultra-low power needs, the system can still provide enough power for communication across different standards, including Bluetooth and 802.15.4.

“A key challenge is designing these circuits with extremely low standby power, because most of these devices are just sitting idling, waiting for some event to trigger a communication,” Chandrakasan told MIT News. “When it’s on, you want to be as efficient as possible, and when it’s off, you want to really cut off the off-state power, the leakage power.”

Chandrakasan said the key was to reduce the leakage of power in the transistor. Even when there is no charge applied to the transistor’s gate, it leaks some current. For devices that mostly sit idle waiting for a signal to power up, the slow leak can take a toll on battery life. (Limiting leakage was a main factor in two fundamental redesigns of transistors in computer processors.)

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