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Memristor — 4th Basic Element of Circuits 291

esocid writes "Researchers at HP Labs have solved a decades-old mystery by proving the existence of a fourth basic element in integrated circuits that could make it possible to develop computers that turn on and off like an electric light. The memristor — short for memory resistor — could make it possible to develop far more energy-efficient computing systems with memories that retain information even after the power is off, so there's no wait for the system to boot up after turning the computer on. It may even be possible to create systems with some of the pattern-matching abilities of the human brain. Leon Chua, a distinguished faculty member at the University of California at Berkeley, initially theorized about and named the element in an academic paper published 37 years ago. Chua argued that the memristor was the fourth fundamental circuit element, along with the resistor, capacitor and inductor, and that it had properties that could not be duplicated by any combination of the other three elements."
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Memristor — 4th Basic Element of Circuits

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  • Great! (Score:2, Funny)

    by teddaman ( 854135 )
    One more thing to wipe after surfing porn.
  • by fahrbot-bot ( 874524 ) on Wednesday April 30, 2008 @06:41PM (#23257388)
    develop ... computing systems with memories that retain information even after the power is off, so there's no wait for the system to boot up after turning the computer on. ... create systems with some of the pattern-matching abilities of the human brain.

    As far as I know, human brains don't retain much information when the power is turned off and there's usually some trouble after the power is restored. Furthermore, I'm not sure how power-down information retention relates to pattern-matching abilities.

    But what to I know, I had my brain off last night.

  • I wouldn't say this is the 4th basic circuit element- that is quite a stretch.

    Basically you have Ohm's law which is v =Ri. There is a component for each variable: Capacitors for voltage, inductors for current, resistors for resistance. It is all there, in nice little differential equations.

    Yes, this is a great discovery. But please stop with the sensationalist headlines. This is getting out of hand.

    • Re: (Score:2, Interesting)

      hmm... electronics component which has a function that can not be duplicated by any combination of the other 3.... seems pretty basic to me. Perhaps Ohm's Law needs a revision, or perhaps it does not cover memristors.
    • by Anonymous Coward on Wednesday April 30, 2008 @06:55PM (#23257576)
      What are you talking about? V does not equate to capacitors any more then it equates to electric generators or batteries. And where on earth did you get inductance as i? In many cases capacitors and inductors behave fairly similarly (baring the fact that inductors have a charge time). If anything inductors relate to a delta i and not i directly.

      Ohms law does not describe the basic componets of a circuit, it only provides a simply way to determine simple information about a simple circuit (Mainly a energy source, and a resistor). It has no room for capacitors or inductors. You need much higher math for that.
      • Re: (Score:3, Informative)

        by Orne ( 144925 )
        Unfortunately, everything about this device seems like higher math. If you bring in the Laplace representation, then Ohm's law becomes:

        V = (R) i + (1/(s C)) i + (s L) i

        This "memristor" is actually a function of the history of the electric flux going through the circuit:

        V = M(q(t)) i, where M is the memristance
        M(q(t)) = d Phi(t) / d q, where q is the electric charge particle
        Phi = electric flux = integral of electric field E over an area A
    • Capacitors don't provide voltage, they resist a change in it. Ditto for inductors & amperage. Although I'll agree it's not the fourth element - it would be the fifth. A NP junction in its various forms would be the fourth.
    • by dfedfe ( 980539 ) on Wednesday April 30, 2008 @07:03PM (#23257666)
      Figure 1 in the paper explains it. The four fundamental circuit variables are current, voltage, charge, and magnetic flux. There are six ways of choosing two of these four, which correspond to differential equations relating the variables. Two of them are "given" in that charge is the time integral of current and magnetic flux the time integral of voltage: dq = idt. dphi = vdt.

      As for the others, they are components. For instance, a resistor R fits in dv = Rdi. A capacitor C fits in as dq = Cdv. An inductor as dphi = Ldi, and a memristor fills in the missing dphi = Mdq.

      • Ah, well that makes sense then.
    • Re: (Score:3, Informative)

      by Chris Burke ( 6130 )
      The only thing covered by Ohm's Law is the resistor, that being the "R" in V = iR.

      For capacitors the equivalent law is i = C (dV/dt), and for inductors it's V = L (di/dt).

      You can combine them all for an RLC circuit, but the result isn't Ohm's law.

    • by mmdog ( 34909 ) *
      I don't know enough to debate it in any depth, but I thought that the laws of physics operated differently or that our understanding of them is incomplete at the nanoscale. Ohm's Law is an example I've seen used in a couple different books about nanotech, both basically saying that when the parts get small enough that the rules as we currently understand them don't really work very well.

      Before the flaming even starts I'll repeat that my knowledge on either physics or nanotechnology is limited. Perhap
  • This sounds like a great advance. However, computers that don't need to be booted or that boot instantaneously is not new.

    TRS-80 Color Computer, for example boots instantly since it runs from ROM unless you are using OS-9.

    The TRS-80 Model 100 keeps its file system in RAM and has a separate NiCD to backup the RAM. It boots instantly. The backup lasts months in my experience (even today with old NiCd's).

    And any computer can simply be left on... no boot time.

    So there's nothing here that cannot be done with a m
    • Both of those computers do jack diddly shit, the Amiga has half its OS in ROM and even when you reboot from the recoverable ramdisk (so you hit the disk for about a second) it still takes a few seconds for things to sort themselves out. Computers more complicated than a digital joystick need a little time.
      • by jhoger ( 519683 )
        Well you're wrong. I can do plenty of interesting applications with both. Text editing and terminal emulation is pretty useful and the Model 100 is very good at both.

        But to conclusively disprove your point, just look at the Palm Pilot. It turns on instantly too.

        Boot time is not a necessity.
        • But to conclusively disprove your point, just look at the Palm Pilot. It turns on instantly too.

          Negative. Palm Pilots do NOT boot instantly. Reset one, and see how long it takes to boot. Those machines hibernate. Ditto for their predecessor, the GRiDPad 2390, which was where Palm Computing got their start. It ran PC-GEOS.

    • by Detritus ( 11846 )
      Both of those examples were preceded by computers with magnetic core memory. When properly designed, they could be loaded with software and turned off, and later turned on, resuming operation almost instantly.
  • Based on the comments above me I'm not the only one who picked up less than nothing from the article...What is it and how does it work? This is less detailed than a Star Trek Particle description.
    • by Otter ( 3800 )
      Article [] and commentary [] at Nature. (I'm not sure whether either or both are subscription-only.)

      The bizarre characterization of this as a discovery instead of an invention originates in the paper itself.

  • Does this mean I will eventually not be able to use "try rebooting the system" (to try and solve a problem)? In all seriousness, I think this will make us rethink our problem-solving approach. Powering-off is a great way to "wipe the slate clean" as it were.

    Would this also inspire new forms of malware/viruses/trojans that persist in memory even after the system is powered off?

    And another thing... forensic computer evidence. I guess you could sort of tell what the user was last doing before they turned off t
  • An engineer, a physicist and a mathematician are staying in a hotel.
    The engineer wakes up and smells smoke. He goes out into the hallway and sees a fire, so he fills a trash can from his room with water and douses the fire. He goes back to bed.
    Later, the physicist wakes up and smells smoke. He opens his door and sees a fire in the hallway. He walks down the hall to a fire hose and after calculating the flame velocity, distance, water pressure, trajectory, etc. extinguishes the fire with the minimum amount of water and energy needed.
    Later, the mathematician wakes up and smells smoke. He goes to the hall, sees the fire and then the fire hose. He thinks for a moment and then exclaims, "Ah, a solution exists!" and then goes back to bed.
    • Must have been one damned persistent arsonist.

      Why would he not use an accelerant ?

      Does this hotel not have smoke alarms ?

      And why would none of them call the fire dept. and / or report the fire to the hotel management ?

      Your story is full of holes.
  • by Chris Burke ( 6130 ) on Wednesday April 30, 2008 @06:46PM (#23257468) Homepage
    I don't understand what makes it a "fundamental" part of a circuit, while say a diode or MOSFET isn't. You can't make a transistor out of resistors, capacitors, and inductors... That's why it always showed up as the magical "voltage-controlled current source" in entry-level circuit analysis courses. I thought the three classic "basic" elements were because they were just the simplest.

    Or maybe they're "basic" because every circuit (that's not superconducting), whether or not it contains semiconductors or more exotic stuff, has some amount resistance, capacitance, and inductance. Even if you don't want it, in which case you call it "parasitic". I don't think you're going to accidentally create two separate layers of titanium oxide.

    So while I get why this discovery is totally awesome, I don't get what they mean by "fourth fundamental circuit element". Anyone got the skinny?
    • Anyone got the skinny?

      Yes but please don't tell anyone. I'm having a hard enough time trying to get girls to like me as it is.
      • Well I could blab about it all I wanted and there's still little chance of a girl finding out, so I think you're safe.
    • by moosesocks ( 264553 ) on Wednesday April 30, 2008 @07:39PM (#23258046) Homepage
      This one took quite a bit of thinking, although this wikipedia article [] summarizes it best.

      A transistor may be approximated as a variable current source. Similarly, many applications of transistors are as "active" devices, which supply external power to the circuit being considered.

      A diode is effectively nothing more than a voltage-controlled switch. In a DC circuit, it simply passes current through (with a small voltage drop that can be approximated by an inline negative voltage source).

      Likewise, all transistors can be abstractly considered as networks of diodes. This is why they are inherently binary devices, and why computers "think" in binary.

      The classical circuit elements (Resistor, Capacitor, Inductor) each fundamentally affect the electromagnetic properties of the electrons flowing through said circuit.

      Resistors impede the flow of current; a capacitor is a current "bucket" that also blocks DC signals in AC circuits; and an inductor builds up a sort of inertia for the flow of current, through the creation of a magnetic field.

      The distinction is hazy, but I think I can see it where it comes from.... when a diode/transistor does something, it affects of the "layout" of the circuit, rather than directly affecting the electrons flowing through it.

      The memristor is extremely interesting, as it blurs the line between analogue components and solid-state devices, and provides exciting possibilities for the development of analogue computing and data storage.

      Even more exciting is that they can already be made smaller than transistors, and two can be combined to create a device that functions analogous to a transistor.

      Considering that we're quickly approaching the limits of Silicon-based technology, this invention may very well offer the key to the true "next generation" of electronic devices, and may very well be as significant to our generation as the transistor was to the previous. This is Nobel Prize-worthy stuff we're talking about.

      Kudos to HP for supporting "true" R&D. They most definitely will be reaping the benefits of this one for years to come.
      • by Komi ( 89040 )
        The distinction is hazy, but I think I can see it where it comes from.... when a diode/transistor does something, it affects of the "layout" of the circuit, rather than directly affecting the electrons flowing through it.

        Not quite correct. A transistor does directly affect the electrons that flow through it. I'm particularly thinking of MOSFETs, which I work with. There's a gate that directly affects how much current will flow through the channel.

        I think the distinction has to do with linearizing the

      • by v1 ( 525388 )
        Resistors I see affecting a circuit immediately. They do make changes, but there is no delay and it's a sort of 1:1 relationship. They "do not change".

        Inductors and capacitors affect a circuit over time. As they are affected more, they produce more effect, and vice versa. They have a sort of memory, but it's usually short term and is the sort of thing that is "used" by the circuit immediately. They "change after awhile".

        Transistors and diodes are different in that they cause distinctly different behavi
    • Diodes and all types of transistors work on the same principle. If this doesn't, then it's something new. If it is, then it's just exploiting formerly misunderstood properties of a transistor. Resistors and capacitors, of course, are completely different from transistors; resistors are just harder to push electrons through and capacitors store them. They're fundamentally different beasts in that we are interested in totally different properties of each (although a transistor certainly has both resistance an
    • I don't understand what makes it a "fundamental" part of a circuit, while say a diode or MOSFET isn't.

      I think what the fundamental elements have in common is that they have a linear transfer function, whereas transistors and diodes are non-linear.
      • "Linear" in what sense? True: you (essentially) get out the same frequencies you put into a system made up of these elements, and there is a (roughly) linear relationship between voltage across and current through these individual components. I'm a bit hesitant to really term them "linear", though, because for a nontrivial definition of "linear", any combinations of them should also be linear, and that's definitely not true: they shift around the poles and singularities of the transfer functions, and the am
        • by aXis100 ( 690904 )
          Linear as in "not discontinuous". Diodes and transistors have knees, gaps and other discontinuities in their voltage / current functions.
    • by Anonymous Coward on Wednesday April 30, 2008 @07:54PM (#23258198)
      I don't get what they mean by "fourth fundamental circuit element"

      There are four fundamental circuit variables; current, voltage, charge, and flux.

      We can define the relationships between charge and current and between flux and voltage. (charge as an integral of current, flux as an integral of voltage over time)

      A resistor provides a function to relate voltage and current.
      A capacitor provides a function to relate charge and voltage.
      An inductor provides a function to relate flux and current.

      Until now we did not know how to construct a passive device which would provide a function relating charge and flux. The only remaining combination of these fundamental variables.
      • That's a good explanation that ties together what I already knew about RLC circuits with the piece that was missing, thank you.
      • by whoever57 ( 658626 ) on Wednesday April 30, 2008 @08:27PM (#23258458) Journal

        between flux and voltage. (charge as an integral of current, flux as an integral of voltage over time)
        According to EETimes, flux is "change in voltage", []rather than an intergral. From the article:

        The hold-up over the last 37 years, according to professor Chua, has been a misconception that has pervaded electronic circuit theory. That misconception is that the fundamental relationship in passive circuitry is between voltage and charge. What the researchers contend is that the fundamental relationship is actually between changes-in-voltage, or flux, and charge.
      • Great Scott! (Score:2, Informative)

        by Anonymous Coward

        A capacitor provides a function to relate charge and voltage.

        ... [this is] a passive device which would provide a function relating charge and flux

        So what you're saying is that it's sorta like a capacitor, but instead of voltage, its function operates on flux.

        How many gigawatts can it handle?

      • by naoursla ( 99850 )
        I wish that hadn't been posted by an anonymous coward. I want to add them as a friend so that their future posts are more visible to me.
      • by IorDMUX ( 870522 )
        An honest question, here...

        I thought that only moving charges, i.e. current, could produce magnetic flux. Is there another method of magnetic flux production going on, here? If it is still flux caused by moving charges, how is it different than the inductor?
    • The three elements we're used to (R, L and C) relate four things, potential, current, flux and charge. R relates current and potential, L current and flux and C potential and charge. The thing that relates flux to charge is this newfangled (compared to the other three) thing called a memristor. The other two relations (potential/flux and current/charge) are fundamental conservation laws.

      At least that's what my quick Googling on the subject turned up.
  • I've just invented the memristor!

    Another grand name from the creator of the finglonger.
  • Repeat after me: the researchers constructed a membristor.

    Somehow, I don't think these scientists really care about the abstract existence of memristors. Moreover, you can't prove the existence of something that didn't exist before you started. You might be able to proved the feasibility of such devices, but only in mathematics it may be appropriate to say you "proved the existence" of something when you actually have a construction.
    • by snarkh ( 118018 )

      Actually, they did not construct it, they proved that it can be constructed using some special properties of nano-particles.
    • Wait.. Are you saying I couldn't prove the existence of monopole by making one? You can mathematically extrapolate its properties until you are blue in the face, but you can't prove its existence in math. Think about particle physics. Our creation of the top Quark, didn't prove its existence?
  • by Tumbleweed ( 3706 ) * on Wednesday April 30, 2008 @06:49PM (#23257500)
    and then we'll have Leeloo and her multi-pass! Totally cannot wait...
  • So there you have it - the four fundamental elements are now earth, air, fire, and memristor. We never really wanted water in our computers anyway, so it's good to eliminate it (and don't even think about water cooling your systems - that's sacrilege).

    This is very interesting stuff. I wonder if these will ever be produced for amateur use, or if they'll only ever find their way into DRAM and such..
  • The possible uses outlined in the article inspire the imagination, but for my money, a technology that remembers everything presents a privacy risk too extreme to contemplate.
    • Re: (Score:3, Interesting)

      Good: You're trying to recognize privacy problems.

      Bad: You apparently don't understand the problem well enough to differentiate problems from non-problems.

  • []

    You'd think the article would link to it.

  • PROM's, EPROM's, EEPROM's, FLASH, etc., have been around for a very long time. Is this "memresistor" different/better because it's denser and cheaper to manufacturer? Unless I missed it, the article never cites any advantage over existing non-volatile memory technologies.
    • Just a guess from what I read, but for one, I would think that where the memory cells of current storage devices require several inter-operating bits and pieces, a memory cell of the future using this technique might pack multiple times the storage capacity into the same chip due to extremely reduced complexity.

      I also wonder if something like this could be used, say, in the manufacture of LED displays where each pixel has dedicated state information. Then we could send packetized bursts of change informat
    • by WarJolt ( 990309 )
      Flash must be written by the block. In binary you zero everything out in the block and write all the ones or visa versa.

      It's slow. It doesn't behave like RAM. It's also got a max number of writes typically expressed in MAX-number of erase cycles.

      Don't know much all the PROMS, but the ones that I'm familiar with are slow.
    • Well, I don't see any reasons why it would not be as fast as SRAM or why it wouldn't be possible to integrate it directly within the CPU. We have chips that contain flash alright, but not right within the core of the CPU. Think registers that are ready for use even after being powered down. This also makes it possible to create cells that retain their information locally even when not operating. At least, that is my interpretation of what they are saying here.

      What I don't understand is the reason why it cou
  • Here: CNet Writeup []

    Discussion of why a memristor is new, and more about how it works.
  • If they mean passive components that function with voltage other than input signals, or devices with only two connections, shouldn't they count diodes? And what integrated circuit actually uses parasitic inductance (that from the bonding wires connecting the chip)? The only semi-real inductance-for-a-purpose I've seen in a monolithic chip isn't available without the chip being powered, and is essentially synthesized by use of capacitance in the feedback loop of an inverting amplifier.

    And if we're cheating
  • The article is very light on actual details, but you could already do this to some degree.

    Resistance of metals can increase with the temperature of the metal (see []). With that, you could try this at home. Take a length of wire, and thermally insulate it. Put a lot of current through it to heat it up. Wait. Read the resistance of the wire later on. The resistance of the wire now is slightly higher than it was (resistivity is rather small, and you would probably only

  • Okay, I RTFA'd, but I still don't get it. Their summary states:

    When a current is applied to one, the resistance of the other changes.

    Now, if I'm correct:

    A) This requires current to flow through the first wire, so where's the memory?
    B) Aside from the probably-more-linear relationship, how is this different from JFET's or BJT's?

    I mean, the transistor is a device where you run a current or voltage to point A, changing the resistance between points B and C. Can someone explain the difference?

  • There's a difference between the memristor and flip-flops and any other device that mimics it. This is one device, not made up of transistors or capacitors, simplifying a circuit considerably. Also it scales beautifully to the nanometer size, allowing for smaller, simpler fast memory without need of capacitors.
  • It seems to me from reading a few articles, that this is a non-linear device. For the record I'm just finishing EE junior year. It seems the applications for these devices are like flip-flops (a la the memory talk) and to act like axons. Using analog analysis on flip flops shows that they are non-linear. (I thought through a few different logics, CMOS, TTL, and diode logic). Axons, as far as I can tell from the internet and Carver Mead's book: Analog VLSI and Neural Systems, are non-linear as well. Why is l
  • Chua argued that the memristor was the fourth fundamental circuit element, along with the resistor, capacitor and inductor, and that it had properties that could not be duplicated by any combination of the other three elements.

    Imagine the possibilities once our computers can remember information! Oh, wait...

  • Memory that could survive power off is old hat, both with various forms of ROM as well as RAM (core memory for example). What makes this new component different?
  • For the curious, here's the research abstract for the article published in Nature (unfortunately, the full article requires a subscription):

    The missing memristor found []

    Dmitri B. Strukov1, Gregory S. Snider1, Duncan R. Stewart1 & R. Stanley Williams1

    Anyone who ever took an electronics laboratory class will be familiar with the fundamental passive circuit elements: the resistor, the capacitor and the inductor. However, in 1971 Leon Chua reasoned from symmetry arguments that there should be a fourth fundamental element, which he called a memristor (short for memory resistor)1. Although he showed that such an element has many interesting and valuable circuit properties, until now no one has presented either a useful physical model or an example of a memristor. Here we show, using a simple analytical example, that memristance arises naturally in nanoscale systems in which solid-state electronic and ionic transport are coupled under an external bias voltage. These results serve as the foundation for understanding a wide range of hysteretic current-voltage behaviour observed in many nanoscale electronic devices2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 that involve the motion of charged atomic or molecular species, in particular certain titanium dioxide cross-point switches20, 21, 22.

    Here's the final paragraph of the research paper, which discusses some of the implications:

    The rich hysteretic i-v characteristics detected in many thin-film, two-terminal devices can now be understood as memristive behaviour defined by coupled equations of motion: some for (ionized) atomic degrees of freedom that define the internal state of the device, and others for the electronic transport. This behaviour is increasingly relevant as the active region in many electronic devices continues to shrink to a width of only a few nanometres, so even a low applied voltage corresponds to a large electric field that can cause charged species to move. Such dopant or impurity motion through the active region can produce dramatic changes in the device resistance. Including memristors and memristive systems in integrated circuits has the potential to significantly extend circuit functionality as long as the dynamical nature of such devices is understood and properly used. Important applications include ultradense, semi-non-volatile memories and learning networks that require a synapse-like function.

    There's also a Nature News and Views [], but I think that might also need a subscription.

  • I suppose 36 years ago "memristor" might have seemed cool. But it just doesn't feel right. Even "memistor" is better than "memristor". For that matter, so is "resimory".

    How about "flasistor" or "resistash"? I know! "Storistor"!! Yeah, that's the ticket!

Research is what I'm doing when I don't know what I'm doing. -- Wernher von Braun