Chapter1 - Digital systems and VLSI Gate Arrays Standard Cells Functional Blocks CMOS Logic 1 Digital systems and VLSI Most other fields of engineering

Chapter1 - Digital systems and VLSI Gate Arrays Standard...

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Digital systems and VLSI Gate Arrays Standard Cells Functional Blocks CMOS Logic 1
Digital systems and VLSI Most other fields of engineering involve trade-offs between performance, power, and price. However, as transistors become smaller, they also become faster, dissipate less power, and are cheaper to manufacture. This synergy has not only revolutionized electronics, but also society at large. Transistors can be viewed as electrically controlled switches with a control terminal and two other terminals that are connected or disconnected depending on the voltage or current applied to the control. Soon after inventing the point contact transistor, Bell Labs developed the bipolar junction transistorBipolar transistors were more reliable, less noisy, and more power-efficient. Early integrated circuits primarily used bipolar transistors. Bipolar transistors require a small current into the control (base) terminal to switch much larger currents between the other two (emitter and collector) terminals
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Digital systems and VLSI cont.…The quiescent power dissipated by these base currents, drawn even when the circuit is not switching, limits the maximum number of transistors that can be integrated onto a single die. By the 1960s, Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) began to enter production. MOSFETs offer the compelling advantage that they draw almost zero control current while idle. They come in two flavours: nMOS and pMOS, using n-type and p-type silicon, respectively.
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Digital systems and VLSI cont.…In 1963, Frank Wanlass at Fairchild described the first logic gates using MOSFETs [Wanlass63]. Fairchild‘s gates used both nMOS and pMOS transistors, earning the name Complementary Metal Oxide Semiconductor, or CMOS. The circuits used discrete transistors but consumed only nano-watts of power, six orders of magnitude less than their bipolar counterparts. With the development of the silicon planar process, MOS integrated circuits became attractive for their low cost because each transistor occupied less area and the fabrication process was simpler [Vadasz69]. Early commercial processes used only pMOS transistors and suffered from poor performance, yield, and reliability. Processes using nMOS transistors became common in the 1970s.
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Digital systems and VLSI cont.…Moore’s Law:- “The number of transistors incorporated in a chip will approximately double every 24 months.”--Gordon Moore, Intel co-founder Moore's law is the observation that the number of transistors in a dense integrated circuit doubles approximately every two years. The observation is named after Gordon E. Moore, the co-founder of Intel and Fairchild Semiconductor, whose 1965 paper described a doubling every year in the number of components per integrated circuit, and projected this rate of growth would continue for at least another decade. In 1975, looking forward to the next decade, he revised the forecast to doubling every two years. His prediction proved accurate for several decades, and the law was used in the semiconductor industry to guide long-term planning and to set targets for research and development. Advancements in digital electronics are strongly linked to Moore's law: quality-adjusted microprocessor prices, memory capacity, sensors and even the number and size of pixels in digital cameras. Moore's law describes a driving force of technological and social change, productivity, and economic growth. The period is often quoted as 18 months because of Intel executive David House, who predicted that chip performance would double every 18 months (being a combination of the effect of more transistors and the transistors being faster).

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