Intelligent Power Amplifiers: Atlanta IC Developer VT Silicon Receives $3.3 Million to Develop WiMax Chips

Atlanta radio-frequency integrated circuit developer VT Silicon has received a $3.3 million round of financing from California-based Menlo Ventures. The Series A funding will help the company design and produce prototypes of its new “intelligent power amplifier” chips for the next-generation of WiMax mobile devices.

Based on silicon-germanium (SiGe) semiconductor materials, the VT Silicon chips will include patent-pending distortion-prevention techniques – known as linearization enhancement – that are designed to support the complex signals used by WiMax devices. To reduce chip costs to justify high-volume consumer applications, the company is building its amplifiers on low-cost SiGe instead of the more exotic – and costly – gallium arsenide (GaAs) materials used in most existing WiMax power amplifiers.

“This funding will allow us to take the linearization techniques we have already proven in a test chip and apply them to commercial chips within the next 9 to 12 months,” said Mike Hooper, VT Silicon’s CEO. “Our plan is to be shipping samples to customers early next year and to begin ramping to production by the middle of next year.”

VT Silicon is a member company of Georgia Tech’s Advanced Technology Development Center (ATDC).

WiMax is intended to provide significantly higher bandwidth and broader coverage for the next generation of mobile devices that will support such applications as streaming video. Sprint Nextel Corp. has already announced plans to roll out WiMax service in large metropolitan areas during 2008, and as a result, manufacturers are rushing to provide the special chipsets the devices need.

That will require some engineering innovation, as the new WiMax mobile devices will demand more power – but be less forgiving of the distortion caused by nonlinear effects that occur at higher power levels, Hooper noted. “They are going up on the complexity curve because they are trying to get more and more information into the same bandwidth.”

Meeting the technical demands in potentially high-volume devices will require new levels of optimization — in addition to new techniques for controlling distortion. VT Silicon has already developed one linearization technique, and is working on others.

“What you want to do is build a power amplifier that is more linear for higher power levels,” Hooper said. “That can give you more range, better battery life and compensate for other issues that you associate with higher performance. Since power amplifiers require a balance of power, linearization, efficiency and other factors, you have to optimize each of these for the specific application where they will be used.”

For its chips, VT Silicon has developed proprietary Linear Enhancement Technology (LET) that will permit the higher power levels. Because SiGe can support both conventional bipolar transistors as well as CMOS, the LET can be implemented on the same chip as the power amplifier, providing cost and design simplicity advantages.

“SiGe affords us the ability to put very sophisticated control and intelligence within the power amplifier because SiGe can combine both CMOS – which is low power control circuitry – and bipolar transistors in one fabrication process,” Hooper noted. “It gives us the ability to get fairly complex, allowing us to make intelligent power amplifiers.”

However, the designers will have to compensate for the relatively lower RF power levels currently produced by most SiGe power ICs. “We have some proprietary technologies to get the power we need,” said Hooper. “We can be competitive with gallium arsenide on power levels.”

The company initially plans to produce two power amplifiers for the WiMax market, operating at 2.5 GHz or 3.5 GHz. As a step toward volume manufacturing, it will work with customers to create a reference design for each prototype chip. Jazz Semiconductor Inc. of Newport Beach, Calif. will produce the chips.

Hal Calhoun, managing director at Menlo Ventures, is bullish on the future of the WiMax market – and VT Silicon’s solutions. “We believe that the leading-edge technology from VT Silicon will be very competitive in this fast-moving market,” he said. “The combination of silicon germanium and unique linearization techniques makes the company’s technology attractive to the key players in this new market.”

Hardware costs will be a significant issue in the success of WiMax, which is just one of the technologies vying for dominance in the next generation of mobile devices. “If the chipsets can be produced inexpensively compared to current WiFi devices, WiMax can supplant WiFi and become the leading technology for mobile broadband applications,” Hooper said.

The company’s most significant challenge, he added, is hiring enough RFIC engineers to meet its growth needs. VT Silicon is trying to hire four engineers in a very tight market for top professionals.

“The industry is rebounding, and RFIC engineers are hard to get,” Hooper said. “Atlanta is becoming a new growth center for semiconductor technology. We hope to create a bigger synergy in semiconductor development in the Atlanta area. We’ve got some very exciting new technologies and need smart people to help bring them to market.”

About VT Silicon: VT Silicon designs and manufactures multi-band radio frequency integrated circuit (RFIC) solutions for the mobile wireless broadband market. The company’s products leverage novel linearization and efficiency enhancement technologies that enable original equipment manufacturers, original design manufacturers and reference design houses to manufacture broadband, highly-efficient, low-cost and small-footprint modules and transceivers. For more information, please visit (

About Menlo Ventures: Menlo Ventures provides long-term capital and management support to early-stage and emerging-growth companies. It is one of Silicon Valley’s oldest venture capital partnerships, and has organized and managed nine venture funds since its inception in 1976. The firm has more than $4 billion under management, and a team with more than 100 years of collective experience in technology, marketing, sales and general management. For more information, please visit (

Research News & Publications Office
Enterprise Innovation Institute
Georgia Institute of Technology
75 Fifth Street, N.W., Suite 314
Atlanta, GA 30308 USA

Media Relations Contact: John Toon (404-894-6986); E-mail: (

Writer: John Toon