VLSI: A Look in the Past, Present and Future Basic building block is the transistor. –Bipolar...
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Transcript of VLSI: A Look in the Past, Present and Future Basic building block is the transistor. –Bipolar...
VLSI: A Look in the Past, Present and Future
• Basic building block is the transistor. – Bipolar Junction Transistor
(BJT), reliable, less noisy and more power efficient. Early integrated circuits used BJTs.
– Quiescent power dissipated by the BJT is high, limiting the number of devices that can be integrated to make a system.
• Is there an alternative?– Metal Oxide Semiconductor
Field Effect Transistor (MOSFET) dates as far back as 1925.
– MOSFETs come in two flavors nMOS (uses n-type dopants) and pMOS (use p-type dopants)
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The Integrated Circuit Building Block
• nMOS and pMOS devices used to construct a circuit form what has come to be known as the Complementary Metal Oxide Semiconductor (CMOS).
• Modelled as switches with ON and OFF positions allow circuits to ideally dissipate no power when OFF and dissipate very little power when in operation.
• First microprocessor to be designed (4004 by Intel) used strictly nMOS technology.
• Before the first microprocessor was designed, Gordon Moore stated that: “The complexity for minimum component costs has increased at a rate of roughly a factor of two per year. Certainly over the short term, this rate can be expected to continue if not to increase. Over longer term, the rate of increase is a bit more uncertain, although there is no reason to believe it will not remain nearly constant for at least 10 years.” -1965.
VLSI Today
• Moore’s Law dictates that device count for microprocessors will double every 18 months. This has been the case for 4 decades since this prediction was made.
• Present day microprocessors exceed 1-billion transistors.– Monticelo (1.72-billion)– Pentium 4 (125 million)– Cell (234 million) -IBM– Ultra SPARC IV (295 million)
• CPU speeds are at 4-5 GHz.
• Most of today’s VLSI based systems use CMOS technology.
• Power dissipation is becoming a major problem in these systems.
• With further scaling we are fast approaching the physical limits of silicon.
• It is projected that by 2018 we will reach the atomic limit of Silicon.
VLSI, ULSI or Tera Scale? The FUTURE
• Are there any alternatives to silicon based electronics?
• The so called emerging technologies.– Carbon nanotubes
– Molecular devices
– Single electron technology
– Quantum dots etc.
• Basically the future is yours to invent.
• CMOS remains the defacto for electronics design as a result we will study CMOS technology.
• Our main objectives:– Understand the MOS device
operation– Build MOS circuits (the
inverter)– Build MOS gates (XOR, AND
etc)– Build MOS sub-system
(Adder, Memory, Decoder)– Study low power and high-
performance issues.
SYSTEM SUB-SYSTEM
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VLSI DESIGN
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