chaos in negative resistance

Discussion in 'General Electronics Chat' started by bhuvanesh, Feb 4, 2014.

  1. bhuvanesh

    Thread Starter Member

    Aug 10, 2013
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    we know voltage divider bias circuit gives the fraction of the input voltage.i seen in a book that with choosing any one of the resistance has negative ,we achieve amplification.what does that negative resistance mean.how does it affect the circuit.explain me basically
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    Negative resistance cannot occur in a passive device. Only an active device can provide amplification. The only device that has negative resistance is a tunnel diode, and yes it can provide amplification.

    Read the wiki and enjoy
    http://en.wikipedia.org/wiki/Tunnel_diode
     
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  3. studiot

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  4. t_n_k

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    Perhaps that should be the only two terminal device. For example, PUT's exhibit negative resistance but aren't two terminal.

    Also how about Gunn diodes?
     
    Last edited: Feb 4, 2014
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  5. studiot

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    Papabravo also said passive devices.

    However I'm not sure the OP is sure exactly what he meant.
     
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  6. nsaspook

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    Aug 27, 2009
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    S-NDR devices are fairly common, a neon bulb has a negative resistance region of operation, even zinc and related metals can have negative resistance curves. What's special about tunnel diodes and similar devices is the stability, controllability and/or speed of negative resistance changes with changes in voltage or current. The depletion zone in a tunnel diode is about 10nm (about the wavelength of 'extreme' ultraviolet) so the charge carriers only have to move tiny distances to tunnel across the energy barrier and cause current to flow in response to changes in bias voltage.

    http://www.sparkbangbuzz.com/els/zincosc-el.htm

    http://en.wikibooks.org/wiki/Circuit_Idea/Negative_Differential_Resistance
     
    Last edited: Feb 4, 2014
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  7. alfacliff

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    Dec 13, 2013
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    an electrical arc also exhibits negative resistance. arc's were used to generate rf years ago. was a cleaner signal than a spark transmitter.
     
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  8. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Regular tungsten incandescent lamps exhibit negative resistance.

    I can remember measuring the cold resistance of a 100 watt bulb with an ohm meter as a child and being completely flummoxed by the low readings obtained, took a while to figure that one out.
     
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  9. t_n_k

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    Don't they rather exhibit positive temperature coefficient of resistance??? That's different to negative resistance.

    Negative resistance at some point on the device V-I characteristic would be characterized by an incremental decrease in voltage in response to an incremental increase in current.
     
    Last edited: Feb 5, 2014
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  10. LvW

    Active Member

    Jun 13, 2013
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    An active circuit which resembles a negative resistance can be realized with one operational amplifier and 3 resistors. The input resistance of such a circuit (negative-impedance converter NIC) has a negative characteristic.
    That means: It acts as a voltage controlled current source whereby the current flows into the controlling node.
    There are two basic NIC types: short-circuit-stable or open-circuit-stable.
    negative resistances are used to compensate damping effects caused by positive resistors (e.g. in filters and oscillators).
    (Remark: "chaos" is something else).
     
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  11. bhuvanesh

    Thread Starter Member

    Aug 10, 2013
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    thank for you all.i understand that somethings cannot be gained until we experience it.again thank you all
     
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