The world's first CMOS power amplifier (PA) for 3G wireless mobile devices was demonstrated today at startup Black Sand Technologies, Inc. (Austin, Texas). A clever architecture allowed the company to recast the role of CMOS transistors into a cascaded structure with adaptive algorithms that rivals the performance of a gallium arsenide 3G PA, but on a less expensive CMOS chip.
"The breakthrough innovation that this team has developed is a power amplifier architecture that uses the smart capabilities of CMOS to solve the voltage breakthrough problem that here-to-fore has been a barrier to CMOS playing competitively in the 3G PA arena," said John Diehl, Chief Executive Officer (CEO).
The company estimates that its CMOS 3G PA will be in mass production by 2010, the first year that 3G mobile phone sales will be larger than 2G sales (see figure).
The problem with casting 3G PA's in silicon, which the experts at Black Sand claim to have overcome, was the size of the voltage swings necessary to ramp the power amplifier up and down as required of 3G, compared to always-on 2G PAs. By cascading CMOS transistors atop each other in a voltage-ladder like structure, Black Sand was able to tolerate the smaller voltage swings available in silicon, compared to gallium arsenide.
"A gallium arsenide device can handle a larger voltage swing before it fails--a CMOS transistor is lower, so it comes into the game handicapped from the prespective of power and efficiency," said Diehl. "But our device uses a differential architecture that stacks transistors in such a way that allows the voltage required to swing over multiple transistors," said Diehl.
The company also claims to have built-in the smarts to protects the CMOS circuits from thermal runaway problems as well as from impedance mismatches, such as touching the antenna with your hand. The chip also integrated onto their CMOS die the six discrete components that are required in addition to a gallium arsenide 3G PA chip, making the CMOS solution both smaller and cheaper, according to Black Sand.
CMOS PAs for 2G phones have already appeared, although the lion's share of the market still goes to gallium arsenide devices. The first 2G CMOS PA was demonstrated by Silicon Laboratories back in 2004. Black Sand was founded in 2005 by three former Silicon Labs' employees: Susanne Paul, chief technologist and architect of Black Sand's chips, Dave Pietruszynski, vice president of engineering and Jim Nohrden vice president of marketing.
The world's first 3G CMOS PA has been in development at Black Sand's since June 2007, when the company got its first round of funding. Black Sand also announced today that it had secured $10 million in second round funding from Northbridge Venture Partners and Austin Ventures, bringing the total investment to $18.2 million. Black Sand will use the second round funding to ramp up mass production of its CMOS power amplifiers and to accelerate the development of additional chips.
Black Sand has yet to announce any customers, but claims it has samples out to mobile phone makers, netbook makers, datacard makers and to other application develpers that use gallium arsenide PAs today.