Memristor

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Memristor The Fourth Fundamental Circuit
Element
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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.

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Introduction

• Currently known fundamental passive elements
  Resistors, Capacitors Inductors.
• Does a 4th passive element exist..?
• Leon O. Chua formulated Memristor theory in his
  paper Memristor-The Missing Circuit Element in
  1971.
• Memistors are passive two terminal circuit
  elements.
• Behaves like a nonlinear resistor with memory.

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What exactly the memristor means?
The memristor is formally defined as a
two-terminal element in which the magnetic flux
Fm 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.
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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. ,
Symbol of memristor
V(t) M(q(t))I(t)
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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.

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Fundamental circuit Elements and Variables.
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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.

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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.

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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.
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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.

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resistance vs. voltage characteristics.
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The working of memristor.
Al/TiO2 or TiOX /Al Sandwich  
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The growth of memristor.
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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 FPGAs can be
  built using memristors.
• Programmable logic and signal processing.

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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.

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

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When it is coming?

• Memristor made to replace flash memory, HP goal
  is to offer them by 2012.
• Memristors will likely to be replace both DRAM
  and hard disks in 2014-to-2016.
• The memristor-based analog computers, that may
  take 20-plus years.

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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.

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THANK YOU