Diode

Discussion in 'Homework Help' started by harikanaidu, Dec 24, 2014.

  1. harikanaidu

    Thread Starter Member

    Nov 28, 2014
    76
    1
    Hi ,can any one tell whether the diode is a passive or active component
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
  3. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
  4. WBahn

    Moderator

    Mar 31, 2012
    17,768
    4,802
    What, in your words, marks the difference between a passive and an active component?
     
  5. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    In the words of one better than I....

    "All active devices control the flow of electrons through them. Some active devices allow a voltage to control this current while other active devices allow another current to do the job. Devices utilizing a static voltage as the controlling signal are, not surprisingly, called voltage-controlled devices. Devices working on the principle of one current controlling another current are known as current-controlled devices. For the record, vacuum tubes are voltage-controlled devices while transistors are made as either voltage-controlled or current controlled types."

    My emphasis added but words from link I provided above.

    My words....
    The equivalent circuit of a passive device does not contain a 'controlled' current or voltage source.
     
  6. WBahn

    Moderator

    Mar 31, 2012
    17,768
    4,802
    There are a few different, and somewhat conflicting, definitions of active and passive electronic components out there, which is one (and just one) of the reasons I asked the OP to explain what her understanding of the difference was.

    If the definition is just that they control the flow of electrons through them, then would photodiodes or light-dependent resistors be considered active devices?

    The distinction that I original learned was that an active device has the ability to increase the power content of the signal while a passive device does not. Using that definition, a diode would not be an active device.

    The Wikipedia article on Electronic Components (http://en.wikipedia.org/wiki/Electronic_component#Active_components) seems consistent with this, but then proceeds to list all diodes as active components (but gives no justification for doing so).

    I'm actually not positive about a truly hard definition and I suspect that for any definition someone could find a device that falls into a gray area, so it is once again important that the context of the question be taken into account.
     
  7. harikanaidu

    Thread Starter Member

    Nov 28, 2014
    76
    1
     
  8. harikanaidu

    Thread Starter Member

    Nov 28, 2014
    76
    1
    As you said active device increases the power....increasing power indicates creating energy but this is not possible according to law of conservation of energy.....
     
  9. WBahn

    Moderator

    Mar 31, 2012
    17,768
    4,802
    If you charge a battery you have increased the energy in the battery. Does this violate the law of the conservation of energy? Of course not. All we have done is taken energy from one place (the coal at the power plant or the gasoline in your car) and put it someplace else (the battery). The same with an active device (say an amplifier). It takes energy from one place (the power supply) and puts it into the signal.
     
    wmodavis likes this.
Loading...