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 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, , that a team at HP Labs led by the scientist R.
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These three elements are used to define the four fundamental circuit variables which are electric current, voltage, charge and magnetic flux. Resistors are used to relate current to voltage, capacitors to relate voltage to charge, and inductors to relate current to magnetic flux, but there was no element which could relate charge to magnetic flux.
To overcome this missing link, scientists came up with a new element called Memristor. These Memristor has the properties of both a memory element and a resistor hence wisely named as Memristor. Memristor is being called as the fourth fundamental component, hence increasing the importance of its innovation. 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 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, , 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. 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. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates.
The effect is greatest between wide, flat, parallel, narrowly separated conductors. An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage.
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes.
They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies. Physical charges cannot pass through the dielectric layer of a capacitor, but rather build up in equal and opposite quantities on the electrodes: as each electron accumulates on the negative plate, one leaves the positive plate. Thus the accumulated charge on the electrodes is equal to the integral of the current, as well as being proportional to the voltage as discussed above.
As with any antiderivative, a constant of integration is added to represent the initial voltage v t0. This is the integral form of the capacitor equation, Taking the derivative of this, and multiplying by C, yields the derivative form, [pic]. The dual of the capacitor is the inductor, which stores energy in the magnetic field rather than the electric field. Its current-voltage relation is obtained by exchanging current and voltage in the capacitor equations and replacing C with the inductance L.
INDUCTOR An inductor or a reactor is a passive electrical component that can store energy in a magnetic field created by the electric current passing through it. Inductors are one of the basic electronic components used in electronics where current and voltage change with time, due to the ability of inductors to delay and reshape alternating currents Inductance L measured in henries is an effect resulting from the magnetic field that forms around a current-carrying conductor that tends to resist changes in the current.
Electric current through the conductor creates a magnetic flux proportional to the current. Inductance is a measure of the amount of EMF generated for a unit change in current. For example, an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. The number of loops, the size of each loop, and the material it is wrapped around all affect the inductance. An inductor opposes changes in current.
An ideal inductor would offer no resistance to a constant direct current; however, only superconducting inductors have truly zero electrical resistance. In general, the relationship between the time-varying voltage v t across an inductor with inductance L and the time-varying current i t passing through it is described by the differential equation: Inductors are used extensively in analog circuits and signal processing. Inductors in conjunction with capacitors and other components form tuned circuits which can emphasize or filter out specific signal frequencies.
Applications range from the use of large inductors in power supplies, which in conjunction with filter capacitors remove residual hums known as the Mains hum or other fluctuations from the direct current output, to the small inductance of the ferrite bead or torus installed around a cable to prevent radio frequency interference from being transmitted down the wire.
Two or more inductors which have coupled magnetic flux form a transformer, which is a fundamental component of every electric utility power grid. The efficiency of a transformer may decrease as the frequency increases due to eddy currents in the core material and skin effect on the windings.
Size of the core can be decreased at higher frequencies and, for this reason, aircraft use hertz alternating current rather than the usual 50 or 60 hertz, allowing a great saving in weight from the use of smaller transformers. An inductor is used as the energy storage device in some switched-mode power supplies. This energy transfer ratio determines the input-voltage to output-voltage ratio. This XL is used in complement with an active semiconductor device to maintain very accurate voltage control.
Inductors are also employed in electrical transmission systems, where they are used to depress voltages from lightning strikes and to limit switching currents and fault current.
In this field, they are more commonly referred to as reactors. Larger value inductors may be simulated by use of gyrator circuits. Thus there should be four basic circuit elements described by the remaining relation between the variables.
The relation between these fundamental elements can be shown as : The relation between the charge and the flux was unknown, and so the device which describes it. This led to the discovery of the fourth fundamental element which describes the above missing relation between Charge And Flux.
He developed mathematical equations to represent the Memristor, which Chua believed would balance the functions of the other three types of circuit elements.
In that we were missing one element to relate charge to magnetic flux. That is where the need for the fourth fundamental element comes in. Theory o Each Memristor is characterized by its memristance function describing the charge-dependent rate of change of flux with charge.
Of course, nonzero current implies instantaneously varying charge. Alternating current, however, may reveal the linear dependence in circuit operation by inducing a measurable voltage without net charge movement—as long as the maximum change in q does not cause much change in M. However, in contrast to ordinary resistors, in which the resistance is permanently fixed, memristance may be programmed or switched to different resistance states based on the history of the voltage applied to the memristance material.
This phenomena can be understood graphically in terms of the relationship between the current flowing through a Memristor and the voltage applied across the Memristor. However, for Memristors a similar graph is a little more complicated.
It illustrates the current vs. Current vs. Voltage curve demonstrating hysteretic effects of memristance. As observed above that two straight line segments are formed within the curve.
These two straight line curves may be interpreted as two distinct resistance states with the remainder of the curve as transition regions between these two states. Thus for voltages within a threshold region -VL2 More essays like this:.
Seminar Report on Memristor
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