Contents:  Introduction  what do you mean by memristor.  Need for memristor.  The types of memristor.  Characteristics of memristor.  The working of memristor.  The growth of memristor.  Applications.  Advantages.  conclusion.

 Currently known fundamental passive elements – Resistors, Capacitors & Inductors.  Does a 4 th passive element exist..?  Leon O. Chua formulated Memristor theory in his paper “Memristor-The Missing Circuit Element” in  Memistors are passive two terminal circuit elements.  Behaves like a nonlinear resistor with memory. Introduction:

What exactly the memristor means…? “The memristor is formally defined as a two-terminal element in which the magnetic flux Φ m between the terminals is a function of the amount of electric charge q that has passed through the device.” Memristance (memory + resistance) is a property of an electrical component that describes the variation in resistance of a component with the flow of charge and also retain its resistance level after power had been shut down.

Symbol of memristor Each memristor is characterized by its memristance function describing the charge-dependent rate of change of flux with charge. From faraday's law, flux and charge are time integral of current and voltage, thus we may write It can be inferred from this that memristance is simply charge-dependent resistance.. i.e., V(t) = M(q(t))*I(t)

Need for memristor.  The three known circuit elements resistor, capacitor and inductor relates four fundamental circuit variables as electric current, voltage, charge and magnetic flux.  But these basic elements failed to relate charge to magnetic flux.  To minimize the circuit complexities.

Fundamental circuit Elements and Variables.

Types of memristor.  Spintronic memristor.  Spin torque transfer magneto resistance.  Titanium dioxide memristor.  Polymeric memristor.  Spin memristive systems.  Magnetic memristive systems.  Resonant tunneling dioxide memristor.

Titanium dioxide memristor  On April 30, 2008, a team at HP Labs led by the scientist R. Stanley Williams announced the discovery of a switching memristor.  The HP device is composed of a thin (50nm) Titanium dioxide film between two electrodes.  It achieves a resistance dependent on the history of current using a chemical mechanism.  Initially there are two layers, one slightly depleted of Oxygen atoms, other non-depleted layer.  The depleted layer has much lower resistance than the non- depleted layer.

17 titanium dioxide memristor lined up in row An atomic force microscope image of a simple circuit with 17 memristors lined up in a row. Each memristor has a bottom wire that contacts one side of the device and a top wire that contacts the opposite side. The devices act as 'memory resistors', with the resistance of each device depending on the amount of charge that has moved through each one. The wires in this image are 50 nm wide, or about 150 atoms in total width.

Characteristics of memristor. Current vs. Voltage characteristics  Unlike the ordinary resistors, in which the resistance is fixed Permanently.  Memristor can be programmed or switched to different resistance by applying the different voltages to the material.

resistance vs. voltage characteristics.

The working of memristor. Al/TiO2 or TiOX /Al “Sandwich”

The growth of memristor.

Applications.  Crossbar latches as transistor replacements.  Non-volatile memory applications.  Low power and remote sensing applications.  New ‘memristor’ could make computers work like human brains.  Memristor make chips cheaper.  Memristor can function in both analog and digital forms.  No need of rebooting.  Lower cost and less complexity FPGA’s can be built using memristors.  Programmable logic and signal processing.

Advantages.  It does not require power to maintain its memory.  A memristor circuit requires lower voltage, less power and less time to turn on than competitive memory like DRAM and flash.  The ability to store and retrieve a vast array of intermediate values also pave the way to a completely different class of computing capabilities like an analog computer in which you don't use 1s and 0s only.

 Memristor-transistor hybrid chip can be used to improve and develop circuit design in easier way.  Replace today’s commonly used dynamic random access memory (DRAM).  Memristors replace transistors in future and acquires smaller space in circuit design.

When it is coming?  Memristor made to replace flash memory, HP goal is to offer them by  Memristors will likely to be replace both DRAM and hard disks in 2014-to  The memristor-based analog computers, that may take 20-plus years.

Conclusion.  Redesigning certain types of circuits to include memristors, it is possible to obtain the same function with fewer components, making the circuit itself less expensive and significantly decreasing its power consumption.  The HP group is looking at developing a memristor-based nonvolatile memory that could be 1000 times faster than magnetic disks and use much less power.  As rightly said by Leon Chua and R.Stanley Williams, memristors are so significant that it would be mandatory to re-write the existing electronics engineering textbooks.  So the memristor qualifies as a fundamental circuit element.