1 Introduction:
The introduction of memristors can lead to a new revolution in the field of computing, with the use of memristors in computing world we can develop computers that can think and analyse like human beings. It is a new electrical component born of theoretical physics. The device, a nanoscale component called a “memristor” requires no power to retain data, which it can store more densely than a hard drive and access about as fast as a computer’s RAM potentially allowing it to replace both components in the future.
1.1 Proposed as a Fourth fundamental component:
· Basic electronics theory teaches that there are three fundamental elements of a passive circuit--resistors, capacitors and inductors.
· But in the 1970s, Leon Chua of the
· Now, a team at Hewlett-Packard led by Stanley Williams,head of Information and Quantum Systems lab at HP Labs, has proven that 'memristance' exists. They developed a mathematical model and a physical example of a memristor.
· Resistive Random Access Memory(RRAMs) will open the floodgates for the memristor.
1.2 How it’s different from other fundamental circuit components:
The reason that the memristor is radically different from the other fundamental circuit elements is that, unlike them, it carries a memory of its past. When you turn off the voltage to the circuit, the memristor still remembers how much charge was applied before and for how long. That's an effect that can't be duplicated by any circuit combination of resistors, capacitors, and inductors, which is why the memristor qualifies as a fundamental circuit element.
1.3 Basic behaviour:
Provide a similar relationship between magnetic flux and charge that a resistor gives between voltage and current. In practice, that would mean it acted like a resistor whose value could vary according to the current passing through it and which would remember that value even after the current disappeared.
1.4 Applications and use:
The new element could pave the way for applications both near- and far-term, from nonvolatile RAM to realistic neural networks. The reason computers have to be rebooted every time they are turned on is that their logic circuits are incapable of holding their bits after the power is shut off. But because a memristor can remember voltages, a memristor-driven computer would arguably never need a reboot. We could leave all our Word files and spreadsheets open when we turn off our computers. Whenever we will turn on our computer , everything will be instantly on the screen exactly the way we left it.”
2 Background and history:
The memristor's story starts nearly four decades ago by IEEE Fellow and nonlinear-circuit-theory pioneer Leon Chua. Examining the relationships between charge and flux in resistors, capacitors, and inductors in a 1971 paper, Chua postulated the existence of a fourth element called the memory resistor. Such a device, he figured, would provide a similar relationship between magnetic flux and charge that a resistor gives between voltage and current. In practice, that would mean it acted like a resistor whose value could vary according to the current passing through it and which would remember that value even after the current disappeared.
But the hypothetical device was mostly written off as a mathematical work. Thirty years later, HP senior fellow Stanley Williams and his group were working on molecular electronics when they started to notice strange behavior in their devices. Williams spent several years reading and rereading Chua's papers. After several years of thinking Williams realized their molecular devices were really memristors.
Chua deduced the existence of memristors from the mathematical relationships between the circuit elements. The four circuit quantities (charge, current, voltage, and magnetic flux) can be related to each other in six ways. Two quantities are covered by basic physical laws, and three are covered by known circuit elements (resistor, capacitor, and inductor), says
Chua actually produced a memristor in the 1970s with an impractical combination of resistors, capacitors, inductors, and amplifiers as a proof of concept. The figure shows the memristor proposed by Chua.
3.1 Classical resistor analogy:
The classic analogy for a resistor is a pipe through which water (electricity) runs. The width of the pipe is analogous to the resistance of the flow of current--the narrower the pipe, the greater the resistance. Normal resistors have an unchanging pipe size. A memristor, on the other hand, changes with the amount of water that gets pushed through. If you push water through the pipe in one direction, the pipe gets larger (less resistive). If you push the water in the other direction, the pipe gets smaller (more resistive) and the memristor remembers this thing. When the water flow is turned off, the pipe size does not change.
Such a mechanism could technically be replicated using transistors and capacitors, but, Williams says,”It takes a lot of transistors and capacitors to do the job of a single memristor.”
3.2 How to realize practically:
Here two layers of a semiconductor, titanium dioxide, sandwiched between electrodes. The bottom layer contains the standard material, which is virtually useless for conducting electricity. The top layer is missing a few oxygen atoms, creating positively charged “bubbles” that make it a conductor.
Running a positive charge through the electrode above this layer pushes some of the charged bubbles into the lower layer (where they stay, until another charge is applied), allowing it to conduct electricity and lowering the electrical resistance of the entire cell. A computer can read information in a memristor cell by measuring how much resistance it has.
Hitting the cell with relatively big zaps switches it from high to low resistance levels that correspond to zero and one for digital data. Using less power can give it some resistance value in-between the extremes. And the results are cumulative. The more often you charge the cell, the lower its resistance—in other words, the stronger its memory becomes. That matches the way neurons build stronger connections over time to make memories stronger (and explains why the more you practice something like piano, the better you get at doing it). Applying a negative charge to the top of the cell reverses the process—a lot of power switches a one to a zero in a digital system. Applying finer amounts of current causes a memory to fade.
4 Practical applications:
It’s a long path between proving something in the lab and selling it at Best Buy.
4.1 Memristors as cache:
Memristors will first show up in the next few years as “cache” that sits between a hard drive and the DRAM memory in PCs. The hard drive could load key data, like the instructions to start up Windows, into the memristor cache, which can dump it into the DRAM far faster than transferring it straight from the hard drive—resulting in lightening-fast boot-ups and quick opening of large files.
4.2 Memristor replacing both hard drive and RAM:
Memristor can hold scads more data than a hard drive and access about as fast as DRAM. It can be used to expand out both ways and can try to eat the heart out of both the DRAM and the hard disk.
4.3 Memristors in CPU
Many processes requiring fuzzy logic, like recognizing a face, are very hard to work out with that yes/no logic of a digital computer. But for an analog computer—like, say, the brain—it’s very easy. So Williams proposes a CPU with multiple processing cores: Some digital for the number crunching that today's computers do so well, and others using analog memristors. Take facial recognition. Someone’s face can change from day to day, and definitely from year to year. But it’s not a drastic change that a yes/no digital system is good at figuring out. It’s a mild difference with some degree of change along a continuum and is perfect for an analog computer.
5 Conclusion:
If memristors can be commercialized, it could lead to very dense, energy-efficient memory chips which will require less transistors, less silicon, and require fewer transistors. The newly found circuit element--called a "memristor," (memory resistor) will enable cell phones to go for weeks without a charge, PCs to start up instantly, and laptops to retain session information long after battery death. It can rikindle the electroinic desing industry, which was fast becoming monotonous and cumbersome.
It will lower prices for customers and will provide higher profits for technology companies.
