# Memristor

Memristors ("memory resistor") are a class of passive two-terminal circuit elements that maintain a functional relationship between the time integrals of current and voltage. This results in resistance that varies depending memristance device. Specifically engineered memristors provide controllable resistance useful for the current connection. Memristor is a special case called "memristive systems", a class of mathematical models useful for certain empirically observed phenomena, such as the firing of neurons. The definition of the memristor is based solely on fundamental circuit variables, similar to the resistor, capacitor, and inductor. Unlike family elements, the nonlinear necessarily memristors can be described by any of a variety of time-varying functions. As a result, memristors non linear time-invariant (LTI) circuit patterns. A linear time-invariant memristor is simply a conventional resistor.
?Memristor theory was formulated by the name of Leon Chua in a document of 1971. Chua believes that fourth existing device to provide conceptual symmetry with the resistor, inductor and capacitor. This symmetry is derived from the basic description passive circuit elements, as defined by a relationship between two of the four key variables of the circuit, that is, voltage, current, charge and discharge. A charging device and linking flux (themselves defined as time integrals current and voltage), which would be the memristor remains hypothetical time. He did acknowledge that other scientists had used fixed nonlinear load flow relationships. However, it would be up to thirty-seven years later, on April 30, 2008, a team at HP Labs led by scientist R. Stanley Williams announced the discovery of a switching memristor. Based on a thin layer of titanium dioxide, is presented as an ideal device approximately. is much simpler than currently popular MOSFET switches and also be able to apply some non-volatile memory in a single device, you can enable nanoscale memristors computer technology. Chua also speculates that may be useful in constructing artificial neural networks

Generally when most people think about electronics, they may initially think of products such as cell phones, radios, laptop computers, etc. others, having some engineering background, may think of resistors, capacitors, etc. which are the basic components necessary for electronics to function. Such basic components are fairly limited in number and each having their own characteristic function.

??????????? Memristor theory was formulated and named by Leon Chua in a 1971 paper. Chua strongly believed that a fourth device existed to provide conceptual symmetry with the resistor, inductor, and capacitor. This symmetry follows from the description of basic passive circuit elements as defined by a relation between two of the four fundamental circuit variables. A device linking charge and flux (themselves defined as time integrals of current and voltage), which would be the memristor, was still hypothetical at the time. However, it would not be until thirty-seven years later, on April 30, 2008, that a team at HP Labs led by the scientist R. Stanley Williams would announce the discovery of a switching memristor. Based on a thin film of titanium dioxide, it has been presented as an approximately ideal device.???
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 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.
The arrangement of these few fundamental circuit components form the basis of almost all of the electronic devices we use in our everyday life. Thus the discovery of a brand new fundamental circuit element is something not to be taken lightly and has the potential to open the door to a brand new type of electronics. HP already has plans to implement memristors in a new type of non-volatile memory which could eventually replace flash and other memory systems.

HISTORY

????????? The transistor was invented in 1925 but lay dormant until finding a corporate champion in BellLabs during the 1950s. Now another groundbreaking electronic circuit may be poised for the same kind of success after laying dormant as an academic curiosity for more than three decades. Hewlett-Packard Labs is trying to bring the memristor, the fourth passive circuit element after the resistor, and the capacitor the inductor into the electronics mainstream. Postulated in 1971, the ?memory resistor? represents a potential revolution in electronic circuit theory similar to the invention of transistor.
The history of the memristor can be traced back to nearly four decades ago when in 1971, Leon Chua, a University of California, Berkeley, engineer predicted that there should be a fourth passive circuit element in addition to the other three known passive elements namely the resistor, the capacitor and the inductor. He called this fourth element a ?memory resistor? or a memristor. Examining the relationship between charge, current, voltage and flux in resistors, capacitors, and inductors in a 1971 paper, Chua postulated the existence of memristor. 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.
Fig1. The Simplest Chua?s Circuit. Fig2. Realization of Four Element Chua?s Circuit, NR is Chua Diode. Fig3. Showing Memristor as Fourth Basic Element. But the hypothetical device was mostly written off as a mathematical dalliance. However, it took more than three decades for the memristor to be discovered and come to life. Thirty years after Chua?s Proposal of this mysterious device, HP senior fellow Stanley Williams and his group were working on molecular electronics when they started to notice strange behavior in their devices. One of his HP collaborators, Greg Snider, then rediscovered Chua's work from 1971. Williams spent several years reading and rereading Chua's papers. It was then that Williams realized that their molecular devices were really memristors.