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does a negative resistance really generate power

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ysenthilece

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How can negative resistance generating power be explained qualitatively .
I saw in some basic circuit theory books tat in a parallel LC circuit , the initial energy
will make it oscillate .But this energy is soon dissipated as heat by the leakage resistances in L & C. A negative resistance is introduced then to cancel out the resistance there, thus producing sustained oscillations..

If this is possible , then we can make every lossy substance into a lossless one by adding a series negative resistance so tat it cancels the series resistance.Then superconductors won't be required i guess ...which has a very low resistance tending to zero...
 

When you do a negative resistence, like in Howland current source for example the operational amplifier supply the energy generated . Superconductor really have low power loss, but when you introduce a virtual negative resistence anyone has to supply the losses, it's the difference.

leomecma
 

When we say that a device exhibits a negative resistance characteristic, it simply means that the derivative (slope) of current with respect to voltage is negative. The neegative resistance characteristic is exhibited over a portion of the overall current vs voltage curve. When the voltage is increased in the negative resistance region, the current decreases. No net power is being generated. An example of such a device is the tunnel diode.
Regards,
Kral
 

Negative resistence never generates power. To create a negative resistence circuit, for example with a transistor, the power is supplied by power supply, not by the transistor. Transistor get power from there to create the negative resistance scenario.

To hill:

A negative resistence is the same as normal resistence, where ohm law applies right, but value of resistence is negative. Off course, is not a standard resistence, to create, you will need to use some special qualities of semiconductors, like triacs, or tunnel diodes, or gyractor circuits.

V=IxR where R is not a positive value.

It's mainly used in oscilator circuits, cause in a tank circuit with a negative resistence, it starts oscilating, cause it's unestable.
 

Hi all...


The negative resistance can be built with active devices such as transistors. For example, in a VCO LC, positive feedback causes that inverse tank voltage biases the transistor gate, pulling more current when LC tank voltage goes down. This aleviates power losses, and a correct gm design can set an stable wave amplitude.

A lumped extracted circuit, shows a -1/gm as a "negative resistance".
 

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