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active devices and passive devices

Discussion in 'Electronic Basics' started by James Hanley, Mar 2, 2005.

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  1. James Hanley

    James Hanley Guest

    i'm looking at the definition for active device


    "active device: A device that requires a source of energy for its
    operation and has an output that is a function of present and past
    input signals. Note: Examples of active devices include controlled
    power supplies, transistors, LEDs, amplifiers, and transmitters."

    what active device has a power source but its output is not a function
    of its input signals?
    Also. An LED doesn't even have input signals does it???!!! I can't
    see why it fits into that definition of active device.

    thanks
     
  2. aman

    aman Guest

    An active device is any type of circuit component with the ability to
    electrically control electron flow (electricity controlling
    electricity). In order for a circuit to be properly called electronic,
    it must contain at least one active device. Components incapable of
    controlling current by means of another electrical signal are called
    passive devices. Resistors, capacitors, inductors, transformers, and
    even diodes are all considered passive devices. Active devices include,
    but are not limited to, vacuum tubes, transistors, silicon-controlled
    rectifiers (SCRs), and TRIACs.

    Hope this helps.
     
  3. Kitchen Man

    Kitchen Man Guest

    You've stumbled into an ongoing debate. I agree (as I think most in the
    industry do) with "aman"'s description, but you'll find other sources
    that will group diodes as active devices. Don't worry too much about
    it.
     
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