Hi Jon,
As far as advantages of GaAs, you are correct. The radio frequency noise can be much less in a GaAs process compared to Silicon. GaAs is poplar in RF front end components for very high frequency receivers that need very good noise performance. However, GaAs is much noisier at low frequencies. So, some GaAs PLL components, which are guided very slowly, do not work as well as silicon parts. GaAs, in general, is faster than normal silicon processes. GaAs also has good switching properties. The GaAs RF Class C power amplifiers are really fast efficient switches matched to the 50 ohm antenna. Digital circuits can be made very fast in GaAs as well.
The problem with GaAs is COST. For a certain performance requirement, there is always a tradeoff between silicon and GaAs at some point. The gap between Si and GaAs has been closing in the last 10 years.
GaAs has found good niches in
1) RF power amps
2) high cost, very fast digital ICs,
3) Low noise amplifiers for sensitive RF front ends.
Now, GaAs is a medium in which products are designed. So, one must look at the whole picture. Good products must still be designed and those designs could vary. Also, those products must be sold and supported. The total score would tell you how well the company would fair in the marketplace.
It seems to me that in the three areas mentioned above, the leaders are:
1) ANAD for Class C power amps(GSM, TDMA, AMPS, PHS systems) and Rockwell for the linear power amps(CDMA).
2) VTSS for the digital high speed ICs.
3) TQNT could be the leader here in low noise amps (LNAs), but I'm just not sure. They have a good line of LNAs. MOT and M/A Com have offerings as well. Many times this is integrated on the receiver IC. GaAs seems needed in Satellite receivers whereas many terrestrial radios don't really need to spend the bucks to get a half of a dB extra out of the design because their antenna temperatures are higher to begin with. Many companies use a single discrete device in the front end to get great performance for a minimum of cost. In that case, there is no IC in GaAs, just one device, probably made by HP or NEC.
I hope this helps.
Rex |
