Searching for a component that increases resistance with voltage

[Etesla]

Hi all, I am in search of some component that acts sort of like a reverse zener diode. I need it to have 'infinite' resistance above voltage X, and act like a short circuit below voltage X. I'm not looking for a circuit that has this functionality, I'm looking for a single component. I don't think such a component exists, but I'm coming to you guys to double check. The closest thing I can think of is maybe a weird PTC thermistor of sorts??? but I would like this device to be voltage driven, not temperature driven.

[Yansi]

This is called negative resistance. There is way to many possibilities to achieve and study this.

You can start with just an opamp and a couple of resistors.

[schmitt trigger]

Let's look at your requirements for a moment.
While the behavior of becoming completely open circuit above a certain threshold is fairly straightforward, let's consider your following statement:

...and act like a short circuit below voltage X.

If the device is indeed a dead-short, or an extremely low impedance, when you attempt  to increase the voltage, Ohm's law indicates that current will also increase.... in this instance it would to sky high values.

Lets assume that you use a beefy mosfet with only 10 milliohm Rds. And you want this circuit to go open circuit above 10 volts.
Well, to raise a 10 milliohm impedance to 10 volts, 1000 amps would require to flow!

[tggzzz]

Hi all, I am in search of some component that acts sort of like a reverse zener diode. I need it to have 'infinite' resistance above voltage X, and act like a short circuit below voltage X. I'm not looking for a circuit that has this functionality, I'm looking for a single component. I don't think such a component exists, but I'm coming to you guys to double check. The closest thing I can think of is maybe a weird PTC thermistor of sorts??? but I would like this device to be voltage driven, not temperature driven.

So, you want a component where 0A flows and there is 0V across it. Then you increase the current to 1A or 1kA and since it s a short circuit there is still 0V across it. 

How do you propose to ever get X volts across it?

[MosherIV]

Hey, lets be nice to Etesla! This is the beginners forum.

As the others have suggested, you will not find a single component to match your requirements.

Why do you not want a circuit?
Frankly, it is the only way to acheive what you have asked for.
A simple voltage detector circuit that opens/closes a relay.

[ArthurDent]

A lot may depend on what the 'fuse' will see for voltage and current and whether it has to have no leakage when open or blown. Check this video to see if this is the type of component you're looking for. It is true that this reacts to the load current so if the load current increases as the voltage increases, this might work. Neither a polyfuse or a regular fuse will do exactly what you describe. More information on what you're actually trying to do would be helpful.

[T3sl4co1l]

Constant current source.

Or actually, more exactly -- are you after negative resistance (at high voltage, the average resistance goes to infinity), or constant current (at high voltage, the incremental resistance goes to infinity)?

Search on these terms (incremental resistance) to see definition and discussion.

Tim

[tggzzz]

The OP has indicated the solution he is looking for, in terms of a device's unattainable ideal V-I characteristics.

If the OP would specify the problem or objective to which such a device might be a solution, we could provide more concrete help.

In most walks of life, technical or non-technical, if we know the reason for the question you will probably get a better answer. Either the answer will be more pertinent to your needs, or perhaps it can suggest a better alternative that you haven’t even considered. Don’t ask “Can you give me a lift into town?” Do ask “Can you give me a lift into town, so I can replace my broken frobnitz?”. The answer might be “There’s a spare frobnitz in the attic”, thus saving time, money, the environment – as well as making some space in the attic.

[martin1454]

Maybe some sort of varistor? They can be hard to find with low enough resistance in low voltage, but can get pretty high resistance in high voltage.

[KMoffett]

Isn't increasing resistance with increasing supply voltage the definition of a "constant current" source?  But then we don't know what Etesla wants to use this for.

Ken

[grifftech]

incandecent lamp

[ArthurDent]

Technically a relay that pulls in at the voltage of interest and disconnects the load across a set of N.C. contacts would work. The problem is this trip point is probably a little broad and finding a relay to match the criteria will not be easy. A series resistor, which adds a second component, could adjust it somewhat . Once the relay pulls in it will hold until the input voltage drops to a much lower value so you'd have hysteresis.

[FriedMule]

First, I am a noob so please bare with me but there is an optocoupler that do the exactly opposite of what you want, but maybe you could get the optocoupler to control a digital potentymeter?

opamp here: https://www.onsemi.com/pub/Collateral/H11F3M-D.pdf

[soldar]

incandecent lamp

Indecent lamp can.

[Kilrah]

Until it pops

[Mattjd]

This is called negative resistance. There is way to many possibilities to achieve and study this.

You can start with just an opamp and a couple of resistors.

When I saw that thumbnail I thought it was going to be some sort of memristor based thing. It wasn't but it was a circuit made by Chua himself at least.

[Brumby]

Technically a relay that pulls in at the voltage of interest and disconnects the load across a set of N.C. contacts would work. The problem is this trip point is probably a little broad and finding a relay to match the criteria will not be easy. A series resistor, which adds a second component, could adjust it somewhat . Once the relay pulls in it will hold until the input voltage drops to a much lower value so you'd have hysteresis.

This idea is the closest I've seen to satisfy the criteria specified - and - it has the added bonus of having the infinite resistance/zero resistance characteristic isolated from the trigger voltage.

Of course, the criteria specified do have a lot to be desired if we really want to offer appropriate suggestions.

If the OP would specify the problem or objective to which such a device might be a solution, we could provide more concrete help.

In most walks of life, technical or non-technical, if we know the reason for the question you will probably get a better answer. Either the answer will be more pertinent to your needs, or perhaps it can suggest a better alternative that you haven’t even considered.

Indeed.