Memristor
Memristors /memˈrɪstɚ/ ("memory resistors") 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 varying according to the device's memristance function. Specifically engineered memristors provide controllable resistance useful for switching current. The memristor is a special case in so-called "memristive systems", a class of mathematical models useful for certain empirically observed phenomena, such as the firing of neurons.[3] The definition of the memristor is based solely on fundamental circuit variables, similar to the resistor, capacitor, and inductor. Unlike those more familiar elements, the necessarily nonlinear memristors may be described by any of a variety of time-varying functions. As a result, memristors do not belong to linear time-invariant (LTI) circuit models. A linear time-invariant memristor is simply a conventional resistor.[4]
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, namely voltage, current, charge and flux.[5] 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. He did acknowledge that other scientists had already used fixed nonlinear flux-charge relationships.[6] 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.[7][8][9] Being much simpler than currently popular MOSFET switches and also able to implement one bit of non-volatile memory in a single device, memristors integrated with transistors may enable nanoscale computer technology. Chua also speculates that they may be useful in the construction of artificial neural networks.[10]
[[Image:Memristor.jpg|thumb|right|225px|
- ^ Bush S, "HP nano device implements memristor", Electronics Weekly 2008-05-02
- ^ Michael Kanellos "HP makes memory from a once-theoretical circuit" 2008-04-30 (Blog entry-not a reliable source)
- ^ Chua, L.O., and Kang, S.M., Memristive Devices and Systems, Proceedings of the IEEE 64, 206, 1976
- ^ Chua, p. 511: ... In the very special case where the memristor Φ-q curve is a straight line, ... the memristor reduces to a linear time-invariant resistor.
- ^ Shearer, J.L., Murphy, A.T., and Richardson, H.H., Introduction to systems dynamics, Addison-Wesley, Reading, Mass., 1967. Figure 4.4.
- ^ Chua, Leon O (September 1971), "Memristor—The Missing Circuit Element", IEEE Transactions on Circuit Theory, CT-18 (5): 507–519, doi:10.1109/TCT.1971.1083337
- ^ Tour, James M; He, Tao (2008), "Electronics: The fourth element", Nature, 453: 42–43, doi:10.1038/453042a
- ^ Strukov, Dmitri B; Snider, Gregory S; Stewart, Duncan R; Williams, Stanley R (2008), "The missing memristor found", Nature, 453: 80–83, doi:10.1038/nature06932
- ^ Marks, Paul (2008-04-30). "Engineers find 'missing link' of electronics". New Scientist. Diakses tanggal 2008-04-30. See also: "Researchers Prove Existence of New Basic Element for Electronic Circuits -- Memristor'". Physorg.com. 2008-04-30. Diakses tanggal 2008-04-30.
- ^ "'Missing link' memristor created". EETimes. 2008-04-30. Diakses tanggal 2008-04-30.