h the same. There are some informed industry observers that consider a tuneable front end defined strictly as a well-behaved device that can access any part of any band anywhere between 700 MHz and 4.2 GHz could be twenty years away. This begs the question as to what the difference would be between say a twenty-five-band device in twenty years time (assuming one band is added each year) and a device with a genuinely flexible 700 MHz to 4.2 GHz front end. From Making Telecoms Work a user-experience perspective the answer is probably not a lot, but the inventory management savings of the infinitely flexible device would be substantial, suggesting that this is an end point still worth pursuing. 5.5.3 Power-Amplifier Material Options RF efficiency is determined by the difficulty of matching the power amplifier to the antenna or multiple antennas and to the switch path or multiple switch paths across broad operational bandwidths. However, transmission efficiency is also influenced by the material and process used for the amplifier itself. Commercialisation of processes such as gallium arsenide in the early 1990s provided gains in power efficiency to offset some of the efficiency loss implicit in working at higher frequencies, 1800 MHz and above, and needing to preserve wanted AM components in the modulated waveform. In some markets, GSM for example, CMOS-based amplifiers helped to drive down costs and provided a good trade off between cost and performance but for most other applications GaAs provided a more optimum cost/performance compromise. This is still true today. WCDMA or LTE is a significantly more onerous design challenge than GSM but CMOS would be an attractive option in terms of power consumption, cost and integration capability if noise and power consumption could be reduced sufficiently. Noise can be reduced by increasing operating voltage. This also helps increase the passive output matching bandwidth of the device. However, good high-frequency performance requires current to flow rapidly through the cons