Pedantic noob here. In the case of a tunnel diode wouldn't that be a negative differential resistance? For a truly negative resistance I would expect the current to become negative, ie. reverse.

https://www.rfcafe.com/references/e...ive-resistance-electronics-world-may-1961.htm

Negative-resistance devices have been with us long before the tunnel diode. Here are descriptions of some of them, along with how and why they operate.

The tunnel diode has turned many minds toward negative resistance for the first time. Negative resistance is not new, but some electronics people just a few years ago had not heard of the phenomenon, or had forgotten what they once learned about it, because they would give a pitched battle on the subject. Always, they challenged, "How can you make any resistance lower than zero?", which only shows that they thought in terms of wiping out resistance, not of changing its sign. Zero resistance is one thing; while negative resistance is something else again.

https://www.rfcafe.com/references/e...tance-devices-electronics-world-july-1963.htm

 

Back in the 90's as high-density DC/DC converters and distributed power architectures spread out into the world, a fun thing popped up to make everyone scramble to find their old control theory text book - negative resistance.

The input to a DC/DC converter with a fixed load appears as a negative resistance to the upstream DC source. For a constant power load, E and I are inversely proportional; as the input voltage increases, the input current drawn decreases. It turns out that if the upstream DC source is a switching power supply or PFC stage, marginal phase margin in the control loop appears, sometimes with gusto.

ak

 

Back in the 90's as high-density DC/DC converters and distributed power architectures spread out into the world, a fun thing popped up to make everyone scramble to find their old control theory text book - negative resistance.

The input to a DC/DC converter with a fixed load appears as a negative resistance to the upstream DC source. For a constant power load, E and I are inversely proportional; as the input voltage increases, the input current drawn decreases. It turns out that if the upstream DC source is a switching power supply or PFC stage, marginal phase margin in the control loop appears, sometimes with gusto.

ak

I've had my issues with this problem.
https://forum.allaboutcircuits.com/threads/dealing-with-negative-resistance.107553/post-823676

 

How much current would you have to put through it to make it dissipate 1/16th of a Watt?

 

How much current would you have to put through it to make it dissipate 1/16th of a Watt?

2.5A

 

In my opinion, two concepts are mixed here.
What is the real resistance of a zero resistance resistor?
What amperage this resistor is designed for?

 

If it has a maximum current rating, and a maximum power rating, then one can calculate its resistance.
One practical outcome from this discussion: If you have a low current track and a high current track which need to cross, do you put the jumper link in the low current track (which would mean that the high-current track would have to be thinned to go under it, increasing its resistance), or do you put the link in the high current track, which adds the resistance of the link and the resistance of the solder, but allows the track to remain as wide as the link?

 

We all know that there is no such thing as a 0Ω resistor.

If we knew the length, cross-sectional area, material used and temperature we could calculate the resistance and add to that the resistance of the ohmic contacts.

For 1/16W power dissipation, here are the currents for resistances decreasing by one order of magnitude:

Ohms Amps
1 0.25
0.1 0.8
0.01 2.5
0.001 8
0.0001 25
0.00001 80
0.000001 250

Pick your resistance.

 

I always understood a 0 ohm resistor to be nothing more than a ceramic body on a straight wire the same diameter as resistor leads.

 

I always understood a 0 ohm resistor to be nothing more than a ceramic body on a straight wire the same diameter as resistor leads.

When we dealt with through-hole components, there were two sorts. One with a ceramic body, made exactly the same way as a standard quarter-watt resistor, and one with a solid cylinder of metal with leads attached. Some suppliers didn't sate which sort they were going to supply. The all-metal type was good for about 5 Amps, the ceramic type much less - it worked as a fuse of about 1A rating. We used to specify the all-metal type but not all suppliers took any notice.