LONDON Is it possible to make a CMOS power amplifier for 3G cell phone applications that can operate with the same power efficiency and robustness as a gallium arsenide version? ACCO Semiconductor (Saint Germain en Laye, France) believes it has found a way to do just that and with its patent applications in hand is hoping to reap the benefits in a multibillion dollar market.
ACCO has been performing design services in the field of RF ICs since 1994. A number of high frequency chips which go out under system company and semiconductor company brand names were actually designed by teams organized by Denis Masliah, founder and chief technology officer of ACCO.
But the company recently made what Masliah described as a "breakthrough" in the use of CMOS for the implementation of power amplifiers. Masliah went to Pond Venture Partners Ltd. (London, England) believing the technology represented a golden opportunity to transform his company from a design services operation into a fabless semiconductor company.
Over 13 years Masliah has built the company up to 46-person operation with about 40 of that number being design engineers. "We've worked with 20 different companies; either system companies that wanted their own chip or doing semiconductor companies' overflow work," said Masliah.
Pond, which does its own due diligence, was sufficiently impressed with ACCO and its CMOS power amplifier to join with Partech International and put up $10 million in venture capital. Half of that money was given to Masliah early in 2007 to pay for the manufacture of prototypes to prove his concept. ACCO was also able to attract Jamie Urquhart, a former chief operating officer at ARM and now a partner with Pond, to take the position of interim CEO.
"We are filing a cluster of patents on a CMOS power amplifier concept. We have solved the breakdown issue in CMOS," Masliah said. CMOS has been used for GSM cell phone PAs and for the PA requirements of Bluetooth and wireless LANs but for the more complex modulation schemes and higher frequencies of evolved 3G communications and WiMax, GaAs or a similar technology has been necessary up until now.
"The main difference between the GaAs-based technologies and the CMOS technology available today for power amplifiers is the breakdown voltage of the devices. In saturated amplifiers, for very high efficiency regime, the voltage across the device can reach 12 volts or more for a 3 volts bias, and in linear amplifiers, the back-off from the saturation makes it also necessary to have an equivalent voltage excursion to limit distortion at the highest power levels," said Masliah.
"Furthermore, it is necessary to accept [impedance] mismatch from the antenna on the devices that can produce a large voltage across the device, and can destroy it if its voltage capability is too low. With the MASMOS technology, we solve this breakdown issue for all available CMOS technologies available for RF today, from 180nm to 65nm. MASMOS has a gain capability equivalent to GaAs-based devices and a breakdown of over 14 volts routinely."
Masliah won't say exactly what MASMOS is, or what ACCO has done to improve the breakdown immunity of CMOS but admitted that MASMOS is more than just design or architecture. But if it is something physical in the process does that make the CMOS non-standard? "This is something we don't want to discuss. It is scalable with technology from 90-nm to 65-nm to 45-nm and so on. It is applicable to any CMOS foundry. It can be done on SOI wafers," said Masliah. "Our goal is to have products in handsets in 2009," he added.