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Help: How to understand this sentence?

Discussion in 'Electronic Basics' started by Loamlo, Jan 14, 2006.

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  1. Loamlo

    Loamlo Guest

    I am reading an article on OP Amp. And there is such a paragraph as

    "Details of op amp input and output structures are also covered in this
    chapter, with emphasis on how such factors potentially impact
    application performance.In some senses, it is logical to categorize op
    amp types into performance and/or application classes, a process that
    works to some degree, but not altogether."

    What's the "performance and/or application classes" mean? Two classes?
    Then what's the "performance class"?

    Thank you very much in advance.
  2. Tim Williams

    Tim Williams Guest

    Keep reading and you'll find out. Performance refers to desirable
    characteristics: noise, input and output currents and voltages, frequency
    capacity, slew rate, etc.

  3. "Performance classes" usually means segregating parts by some
    specific property/properties of the parts; speed, bandwidth, temp range,
    and like that.

    "Application classes" usually means other engineers have tried
    various parts in various apps and found that certain parts are better
    than others in specific apps because of the particular combination of
    properties a given part has. It may also mean that a class of parts was
    specifically designed to optimize properties desired for say lock-in
    amps or whatever.

    "Not altogether" comes in because often you can't just plug somebody
    else's recommendation for say an instrument amp into your design because
    you may have a different temp range spec or whatever; you may have to
    wade back into the "performance" specs and end up selecting a part
    designed for a different purpose.

    Keyword for the day; "tradeoffs".

    Mark L. Fergerson
  4. Loamlo

    Loamlo Guest

    Thank you very much for answering my questions.
    And now I can understand what's that mean.
  5. You're very welcome.
    Just part of getting from textbooks to reality. Expect more of the
    same as you go along.

    Mark L. Fergerson
  6. Loamlo wrote:

    Do you need a particularly high input impedance from a FET input or does
    bipolar suffice? Is a particularly low noise level required, or would
    you prefer high output current or may be a high slew rate instead? Do
    you want single-rail operation? Do you need the max. output voltage to
    be close to the supply voltage or would a little lower do?

    An introduction to OpAmps will cover the so called "ideal OpAmp" with
    infinite input impedance, zero output impedance, infinite slew rate, no
    bias, no noise and so on. Real OpAmps are technical compromises that
    come close to some of those features, at the expense of others.
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