Design Article
CMOS is the right technology for 3G handset PAs
Brad Fluke, Javelin Semiconductor
2/18/2010 7:41 PM EST
A 3G power amplifier (PA) has the challenging requirement of maintaining linearity while delivering over a watt of peak power at frequencies up to 2 GHz. Today's suppliers of 3G PAs utilize various forms of the process technology gallium arsenide (GaAs) to meet the stringent frequency and voltage swing requirements of the cellular PA. With today's push towards 3G smartphones with multiple radios and global roaming capability, the need for PA innovation has never been greater.
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| Brad Fluke Javelin Semiconductor |
History has shown that once CMOS can meet the difficult analog performance requirements presented by an application, it always wins. A rapid migration to CMOS happens because the flexibility of CMOS leads to improvements in performance, creates the opportunity for new levels of integration and moves the manufacturing supply from small, captive wafer fabrication lines to mainstream wafer foundries where the highest quality and largest capacity can be realized. Past examples of this transition include modem AFEs, data converters, disk drive read channels, wireless transceivers, SLICs and optical networking ICs.
The fundamental advantage of CMOS is flexibility. With the availability of high performance complementary devices, CMOS designers have a richer design toolbox. For PA applications, this enables new topologies that overcome the assumed limitations of CMOS. Also with CMOS, many functions can be easily integrated into a single PA die, such as precision voltage and current references and process tracking circuits. With CMOS, digital circuitry is essentially free, so appropriate application can provide new solutions to old problems. With these advantages, CMOS can provide a better overall answer to the 3G PA challenge.
Previous CMOS PA attempts have failed to meet the performance level of the GaAs incumbents, falling short in areas like power-added efficiency, noise and reliability, plus they utilized expensive IC packaging and had high bill of material costs. Javelin Semiconductor's engineers have broken new ground by developing a pure CMOS implementation that outperforms GaAs PAs, while delivering new levels of reliability and robustness in a low cost commodity package.
Due to the known flexibility, reliability and manufacturing advantages of CMOS, it is the optimal process technology to meet the challenges presented by the PA function in 3G/4G cellular handsets.
Brad Fluke is the CEO of wireless mixed signal IC vendor Javelin Semiconductor Inc. (Austin, Texas).
See other articles in this Point/Counterpoint series:
Point/Counterpoint: Is CMOS right for 3G handset PAs?
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XRF
2/19/2010 2:05 PM EST
Silicon has a reputation of offering the best $ value to the end customer. It has the highest integration capability in the semiconductor industry. Many PA designs, C-MOS or GaAs, have several C-MOS devices around them now. So the real argument is can GaAs close the high level of integration offered by Silicon today. The only drawback is the die shrink which occurs during the lifetime. Power scale does not easily shrink without reliability issues. Overall silicon has the advantage over GaAs even though GaAs can integrate RF matching networks in a smaller scale. Power handling and reliability capabilities of these will need more research from both technologies.
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