07-06-2012, 05:28 PM
MEMRISTOR
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What Are Memristors?
Memristors are basically a fourth class of electrical circuit, joining the resistor, the capacitor, and the inductor, that exhibit their unique properties primarily within the nanoscale. Theoretically, Memristors, a concatenation of “memory resistors”, are a type of passive circuit elements that maintain a relationship between the time integrals of current and voltage across a two terminal element. Thus, a memristors resistance varies according to a devices memristance function. The memristor symbol
Physical restrictions on M (q )
An applied constant voltage potential results in uniformly increasing Φm. numerically, infinite memory resources, or an infinitely strong field, would be required to store a number which grows arbitrarily large. Three alternatives avoid this physical impossibility.
• M (q) approaches zero, such that Φm = ∫M (q) dq = ∫M(q(t))I dt remains bounded but continues changing at an ever-decreasing rate. Eventually, this would encounter some kind of quantization and non-ideal behavior.
• Memristive systems:
The memristor is a special case of a more. General class of nonlinear dynamical devices
Called memristive system . Whether physically realized or not, since memristance was first proposed the memristor has been successfully used as a conceptual tool for analyzing signal processing and for modeling the workings of, for instance, electrochemical and nonlinear semiconductor devices memristor was generalized to memristive systems in a 1976 paper by Leon Chua.
Resonant tunneling diode memristor:
In 1994, F. A. Buot and A. K. Rajagopal of the U.S. Naval Research Laboratory demonstrated [28] that a ‘bow-tie’ current-voltage (I-V) characteristics occurs in AlAs/GaAs/AlAs quantum-well diodes containing special doping design of the spacer layers in the source and drain regions, in agreement with the published experimental results. [29] This ‘bow-tie’ current-voltage (I-V) characteristic is sine qua non of a memristor although the term memristor is not explicitly mentioned in their papers. No magnetic interaction is involved in the analysis of the ‘bow-tie’ I-V characteristics.
Titanium dioxide memristor:
Interest in the memristor revived in 2008 when an experimental solid state version was reported by R. Stanley Williams of Hewlett Packard. The article was the first to demonstrate that a solid-state device could have the characteristics of a memristor based on the behavior of nanoscale thin films. The device neither uses magnetic flux as the theoretical memristor suggested, nor do stores charge as a capacitor does, but instead achieves a resistance dependent on the history of current.
