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New Transistors Give iPad Air 57% Improved Display Efficiency

By Wesley Fenlon

The iPad Air's display is much more efficient than the last generation's, though more efficient display technology is already on the market in devices like the Kindle Fire 8.9.

According to DisplayMate's latest tablet display shoot-out, Apple's new iPad Air boasts a 57 percent bump in display power efficiency over Apple's previous iPads. Every hardware generation tends to be more efficient than the last. Apple improves its software to perform tasks more quickly and in fewer CPU cycles--that's a big draw of OS X Mavericks. Improved CPUs and wireless chips are often able to handle more data while drawing less power. But 57 percent in display efficiency is a big bump, and the iPad Air owes that improvement to a new transistor material called IGZO.

"Displays featuring 'backplanes' of IGZO transistors should make it possible for tablets and TVs to have much higher-resolution displays while consuming significantly less power," explains Technology Review. "The technology has already cropped up in low volumes of high-end smartphones and televisions, but its appearance in iPads suggests we can expect IGZO to improve several more popular products over the next year."

Photo credit: ifixit

Let's back up a second here. Transistors supply electric current to LCD screens, and most LCDs are powered by amorphous silicon transistors. As display makers have chased after higher resolution panels, amorphous silicon has started to become a roadblock. Technology Review explains that "display makers have run up against the physical limits of amorphous silicon, because electrons don’t move through that material fast enough. If transistors can be made from a material with a higher degree of 'electron mobility,' the transistors can be smaller, making it possible to pack more pixels into a given space."

IGZO, or indium gallium zinc oxide, transistors, have that higher degree of electron mobility. Ten times better than amorphous silicon, in fact. And as more displays push into super high resolution territory, we'll likely see more and more of IGZO, which will be great for battery life. However, Technology Review notes that IGZO isn't actually the most efficient transistor material around, and the iPad Air is hardly the first to make use of IGZO.

Some competing devices, including the Amazon Kindle Fire 8.9, use a material called LTPS, or low-temperature polysilicon. DisplayMate's tests show how efficient LTPS can be:

"The Relative Power Efficiency (for the same Luminance and screen area) is highest for the Kindle Fire HDX 8.9, which has the highest performance and most efficient LTPS Low Temperature Poly Silicon LCD. Second is the iPad Air, which has a new higher efficiency metal oxide IGZO LCD that is a 57 percent improvement over the previous iPads, which used a-Si amorphous Silicon, but it still needs 30 percent more display power than the LTPS Kindle Fire. Coming in last in Relative Power Efficiency is the Nexus 10 with an a-Si amorphous Silicon backplane that is used in most current LCD displays, which requires 73 percent more display power than the LTPS Kindle Fire."

LTPS is more power efficient than IGZO, though more expensive and not as easy to implement in larger displays. Clearly IGZO is a step in the right direction, but it may end up as an intermediary technology between amorphous silicon and LTPS--something for 10-inch tablets and cheaper smartphones to adot for the next few years, before LTPS (or perhaps something even more efficient) becomes the dominant display transistor.