chaos in negative resistance

Thread Starter

bhuvanesh

Joined Aug 10, 2013
268
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
 

t_n_k

Joined Mar 6, 2009
5,448
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
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:

studiot

Joined Nov 9, 2007
5,002
For example, PUT's exhibit negative resistance but aren't two terminal.

Also how about Gunn diodes?
Papabravo also said passive devices.

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

nsaspook

Joined Aug 27, 2009
6,260
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
 
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alfacliff

Joined Dec 13, 2013
2,449
an electrical arc also exhibits negative resistance. arc's were used to generate rf years ago. was a cleaner signal than a spark transmitter.
 

Sensacell

Joined Jun 19, 2012
2,437
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.
 

t_n_k

Joined Mar 6, 2009
5,448
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.
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.
 
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LvW

Joined Jun 13, 2013
842
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
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).
 

Thread Starter

bhuvanesh

Joined Aug 10, 2013
268
thank for you all.i understand that somethings cannot be gained until we experience it.again thank you all
 
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