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A bit about analog, and a bit about bits

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Title: Acoustical Imaging Using Capacitive Micromachined Ultrasonic Transducer Arrays: Devices, Circuits, and Systems Author: Omer Oralkan Last modified by – PowerPoint PPT presentation

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Title: A bit about analog, and a bit about bits


1
A bit about analog,and a bit about bits
  • Prof. Tom Lee
  • Stanford University
  • Matrix Semiconductor
  • tomlee_at_ee.stanford.edu
  • http//www-smirc.stanford.edu

2
What is analog, anyway?
  • Analog quantities such as voltage, temperature,
    and pressure span a continuum of values.
  • Signals can range from, say, WiFi microvolts to
    power line megavolts.
  • Analog systems typically evince high
    functionality per unit power consumed (e.g., the
    human ear consumes tens of microwatts), but
  • Difficult to process and store analog signals
    faithfully.
  • Analog functions are usually highly specialized
    typically cant readily convert one analog
    circuit into another one.
  • Nature is analog.

3
What, then, is digital?
  • Digital signals are discrete in amplitude and in
    time
  • Signals are of uniform amplitude, say.
  • Digital systems typically consume high power per
    function, but
  • Storage and replication may be performed
    essentially without error.
  • Digital systems can be quite flexible.
  • Paradoxically, this property has killed off
    circuit design innovation.
  • Digital is unnatural.

4
Analog vs. digital A false dichotomy
  • Analog processing of some kind is unavoidable at
    interfaces with the physical world.
  • No such thing as an all-digital radio, for
    example (despite the buzz about software
    radios).
  • Digital processing is a powerful and flexible way
    of transforming, storing, conveying and
    regenerating information.
  • Cant expect a 100th-generation photocopy to
    resemble the original, but a 100th-generation
    CD-ROM can be just as good as the master.
  • Analog and digital are good at quite different
    things.
  • Explains why the arc of history has traced an
    increasing synthesis of these two.

5
Increasing symbiosis through the ages
6
Increasing symbiosis through the ages
7
Increasing symbiosis through the ages
8
Another 3-D imaging with 2-D CMUTs
9
What you can do with a CMUT
Mechanically scanned transducer Analog processing
2-D electronically scanned array Massive digital
processing
10
So, (why) is analog ascending?
  • Purely digital paradigms are limited.
  • The Pentium 4 consumes 100W, the human brain but
    25W.

11
Biology has thrown down the gauntlet
Source Hans Moravec, CMU
12
Whither analog?
  • One view Analog will serve as merely another
    rationale for Intel to build ever-more powerful
    CPUs. This co-dependency will continue until
    market forces dictate otherwise.
  • Another view Insights gained from studying
    diverse fields will inform, and drive, a
    convergent evolution of seemingly disparate
    technologies.
  • Hard to predict where this will go, but my guess
    is that ethicists and social scientists will have
    plenty to chew on.

13
Man is the only computer that can be
mass-produced by unskilled labor.
-Wernher von Braun, rocket scientist
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