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CMOS Technology and Logic Gates
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6.884 – Spring 2005
2/07/2005
L03 – CMOS Technology 1
Quality of Design
Quality of a hardware design primarily judged by:
– Price
– Performance
– Power and/or Energy
Other important metrics can include:
– Operating range
• Temperature, voltage, background radiation
– Reliability
• Mean-time between failures (MTBF)
– Form factor
• Size, weight
– Flexibility
• Tolerance to changes in specification
Need to understand implementation technology to understand
tradeoffs among these attributes.
6.884 – Spring 2005
2/07/2005
L03 – CMOS Technology 2
System-Level Impacts
Chips do not exist in a vacuum, e.g.,
2/2.5G cell phone contains:
• RISC Application Processor (ARM)
• Digital Signal Processor
• SRAM/DRAM Chips
• Flash Memory Chips
Image removed due to copyright restrictions.
• Analog Chips
– E.g. headphone amplifier
• Radio Chips
• Power Management Subsystem
• Passive components
– resistors, capacitors and
inductors
Digital IC in
Need to consider quality of a design
Package
in context of target system.
– E.g., design alternative might
have twice the performance but
require 10x off-chip memory
bandwidth.
[Buss, ISSCC 2002]
6.884 – Spring 2005
2/07/2005
L03 – CMOS Technology 3
Digital Technology Generations
• Electromechanical Relays
• Vacuum Tubes
• Bipolar Transistors
• CMOS/FET Transistors
– ~10,000nm gates originally, now down to 90nm in production
– scaling will stop somewhere below 30nm (over 100 billion
trans./chip)
• Future:
– 3D CMOS (10 trillion transistors/system?)
– Carbon Nanotubes?
– Molecular Electronics?
CMOS VLSI is
the
digital implementation technology of choice for
the foreseeable future (next 10-20 years)
– Excellent energy versus delay characteristics
– High density of wires and transistors
– Monolithic manufacturing of devices and interconnect, cheap!
6.884 – Spring 2005
2/07/2005
L03 – CMOS Technology 4
Abstraction Levels in Design
Application
Physics
Gap too large to
bridge in one step
but there are exceptions,
e.g. magnetic compass
6.884 – Spring 2005
2/07/2005
L03 – CMOS Technology 5