The first transistor was invented in the 1940s and

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The first transistor was invented in the 1940s and rapidly displaced vacuum tubes. It exhibited a very long (in principle, infinite) lifetime and occupied a much smaller volume (e.g., less than 1 in packaged form) than vacuum tubes did. But it was not until 1960s that the field of microelectronics, i.e., the science of integrating many transistors on one chip, began. Early “integrated circuits” (ICs) contained only a handful of devices, but advances in the technology soon made it possible to dramatically increase the complexity of “microchips.” Example 1.1 Today’s microprocessors contain about 100 million transistors in a chip area of approximately 3 cm. (The chip is a few hundred microns thick.) Suppose integrated circuits were not invented and we attempted to build a processor using 100 million “discrete” transistors. If each device occupies a volume of 3 mm mm mm, determine the minimum volume for the processor. What other issues would arise in such an implementation? Solution The minimum volume is given by 27 mm , i.e., a cube 1.4 m on each side! Of course, the 1
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BR Wiley/Razavi/ Fundamentals of Microelectronics [Razavi.cls v. 2006] June 30, 2007 at 13:42 2 (1) 2 Chap. 1 Introduction to Microelectronics wires connecting the transistors would increase the volume substantially. In addition to occupying a large volume, this discrete processor would be extremely slow ; the signals would need to travel on wires as long as 1.4 m! Furthermore, if each discrete transistor costs 1 cent and weighs 1 g, each processor unit would be priced at one million dollars and weigh 100 tons! Exercise How much power would such a system consume if each transistor dissipates 10 W? This book deals with mostly microelectronics while providing sufficient foundation for gen- eral (perhaps discrete) electronic systems as well. 1.2 Examples of Electronic Systems At this point, we introduce two examples of microelectronic systems and identify some of the important building blocks that we should study in basic electronics. 1.2.1 Cellular Telephone Cellular telephones were developed in the 1980s and rapidly became popular in the 1990s. To- day’s cellphones contain a great deal of sophisticated analog and digital electronics that lie well beyond the scope of this book. But our objective here is to see how the concepts described in this book prove relevant to the operation of a cellphone. Suppose you are speaking with a friend on your cellphone. Your voice is converted to an elec- tric signal by a microphone and, after some processing, transmitted by the antenna. The signal produced by your antenna is picked up by the your friend’s receiver and, after some processing, applied to the speaker [Fig. 1.1(a)]. What goes on in these black boxes? Why are they needed? Microphone ? Speaker Transmitter (TX) (a) (b) Receiver (RX) ?
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