n CMOS (complementary metal-oxide-semiconductor) or SiGe (silicon germanium) or GaAs (gallium arsenide) semiconductor processes. Simplifying a rather complex story, CMOS is lower cost and supports more aggressive integration but does not perform as well as GaAs particularly at higher frequencies. SiGe combines some of the advantages of CMOS and GaAs. GaAs also has some advantages in terms of delivering a better linearity/amplifier efficiency trade off, an important metric for UMTS and LTE and related technologies using a combination of phase and amplitude modulation. The requirement specifically is to deliver good linearity and efficiency at maximum power and good efficiency at minimum power. Telecommunications Economies of Scale Table 4.7 Linearity requirements by technology Peak to average Power control Generation Technology ratio (dB) dynamic range 25 dB ETACS 25 dB JTACS 25 dB 30 dB 30 dB TDMA/EDGE 35 dB UMTS rel 99 80 dB UMTS rel 6/7 35 dB UTRAN/LTE Release 8,9,10,11,12 8-17 (includes multicarrier bonded channel options) An optimum PA (power-amplifier) technology choice for 3.5 GHz is unlikely to be the same as an optimum PA technology choice for 700 MHz. As a general rule, it gets harder to deliver gain without introducing excessive noise as frequency increases. An optimum PA technology choice for GSM is unlikely to be the same as an optimum PA technology choice for UMTS that requires more linearity to preserve the AM (amplitude-modulation) characteristics in the modulated signal envelope. Table 4.7 shows the overall trends over the past 20 years (first- and second-generation cellular) and likely trends over the next five to ten years in terms of the peak to average ratio of the modulated signal envelope (which determines the amount of linearity needed in the amplifier) and the power control dynamic range (which determines the upper and lower power outputs required from the device). GSMK was chosen for GSM because the modulated signal envelope has no intentional amplitude modulation and could/can therefore 