Electronic Design

Reverse Outsourcing May Be Best News Of The Year

This year's most engaging news came from a briefing by Julian Hayes of Wolfson Microelectronics, Edinburgh, Scotland, in September. Walking through the company's-plant, I saw a flat-screen TV disassembledon an engineer's bench. Wolfson was helping a Chinese customer optimize its use of some of the company's audio chips.

The number of subassemblies in the design surprised me. "This doesn't look like a low-margin product designed to sell on price alone at discount outlets," I said. "There's a lot of NRE and manufacturing overhead here, not to mention you and your customer are working recursively on the design like this."

Julian quickly set my prejudices straight. More and more, he said, the Chinese are following the rest of Asia in turning to a business model based on branding. That implies repeat sales based on end-user satisfaction with quality and reliability, and not just on sales price.

The implication is that not all engineering jobs in North America and Europe are necessarily moving to Asia—at least not real real soon. Wolfson proves that when you've got the expertise, you can see reverse outsourcing. Perhaps in the long run, increasing self-fueled prosperity in the Far East will float everybody's boat.

SOLAR ECONOMICS
As I reported in January, grid-connected solar power is on the rise in the U.S., largely due to the issuance of standards for grid-connect inverters. For the past five years, the compound annual growth rate has been over 40%. Last year, the rate reached over 50%. This year, solar-cell efficiency got a big boost when SunPower, a Cypress Semiconductor subsidiary, announced commercial crystal-silicon cells with efficiencies greater than 20% (see the figure). SunPower's gain in efficiency comes from moving the collection grid to the back of the cell, where it doesn't block any light. The conductors in the grid also are made thicker, reducing ohmic losses. Why hasn't this been done before? The back-contact approach means that minority carriers must diffuse through the entire wafer thickness to reach the collecting junctions. In turn, this implies a carrier lifetime of greater than 1 ms. That has only been made possible by the availability of extraordinarily high-lifetime float-zone silicon starting material from the Danish company Topsil Semiconductor Materials A/S.

To make the cells competitively manufacturable, SunPower also developed low-cost screen-printing technology to replace photolithography and adapted diffusion furnaces, wet etching, and cleaning equipment. Four production lines are now up and running in the Philippines.

HOW DO YOU WANT YOUR THRESHOLD VOLTAGE?
The year's most intriguing announcements about discretes came from Advanced Linear Devices. ALD applied its EPAD technology to a pair of matched small-signal enhancement-mode and depletion-mode FETs on a common die, whose floating gates are programmed like E2PROMs to control the threshold voltage. (There also is a dual version.) As a result, the device doesn't require input-signal biasing.

On the first devices, announced last summer, gate-source threshold voltage is essentially zero, rather than around 0.7 V. Later, the company announced products with preprogrammed +0.20-V (±0.02 V), +0.80-V (±0.01 or ±0.02 V), and +1.40-V (±0.04 V) thresholds. They also feature low input bias current (less than 30 pA at 25°C), low input capacitance, and fast switching speed. Using them, designers can build rail-to-rail amplifiers and inverters that operate from voltages as low as that put out by a single solar cell, which typically puts out only around 0.45 V under load.

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