doubt in active device

Discussion in 'General Electronics Chat' started by bhuvanesh, Apr 13, 2014.

  1. bhuvanesh

    Thread Starter Member

    Aug 10, 2013
    268
    2
    Code ( (Unknown Language)):
    1. Those devices or components which produce energy in the form of Voltage or Current are called as Active Components
    how diode produce power
     
    Last edited: Apr 13, 2014
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Where is the reference from?
     
  3. bhuvanesh

    Thread Starter Member

    Aug 10, 2013
    268
    2
  4. MrChips

    Moderator

    Oct 2, 2009
    12,420
    3,355
    In my opinion, the definition in that link is incorrect.

    I would classify a diode as a passive component.
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    I don't understand.

    The quote you pasted into post#1 says the opposite of what is says in your link which is correct, but a roundabout way of stating things.

    Post 1

    An active device is a device which produces energy.........This is wrong

    Link to electricaltechnology.org

    An active device requires an external power supply..........Correct

    But what is does not say is what an active device does with that external power.

    A diode is an active device. For example an LED produces light from the supplied external power.
     
    Last edited: Apr 13, 2014
  6. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    A diode is a passive device, NOT an active device. Even active devices do NOT produce power.
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,516
    1,246
    Technically, nothing produces power since energy can be neither created nor destroyed. What we call power production really is conversion. Power plants convert chemical or nuclear or kinetic energy into electrical enrgy.

    In the context of this thread, tubes, transistors and ICs are active devices since they perform their own kind of energy conversion. Resistors, capacitors, and inductors are the traditional passive devices. Diodes are somewhere in the middle, and LED's came along 100 years after all of this was worked out so I don't know what their official category is. If I have only two choices, then all diodes are active devices. That doesn't smell right, since there is no way a collection of diodes can convert an audio signal into 50 W of audio, but all traditional passives conduct both ways.

    ak
     
  8. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Are you saying a Gunn diode amplifier is not an active device?
     
  9. crutschow

    Expert

    Mar 14, 2008
    12,986
    3,226
    I would classify any semiconductor device as active. I think that any electrical device that isn't passive is active, and the only passive devices of importance are (basically) linear resistors, capacitors and inductors or variations of those, such as transformers. By that definition even a carbon mic is active.
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Since there seems to be some confusion about the difference between active and passive here is a modern explanation.

    An active device can control (or be used to control) at least one of the circuit variables. These are normally currents and voltages.
    That is the active device can determine the value of the circuit variable independently of the rest of the circuit.

    A passive device cannot control any circuit variables. All are determined by the rest of the circuit.

    So in the case of a diode v a resistor in the diagram the circuit can determine the current, I, through the DUT (device under test) and thus the voltage drop, Vab, across a resistor. That is to say it is not independent of the current.

    However the Voltage drop across a diode is constant regardless of the current I through it.

    That is what makes any general purpose diode active and any general purpose resistor passive.
     
Loading...