1. MEMRISTOR
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2. Known Three fundamental passive circuit elements:
Resistor, Inductor, Capacitor.
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3. Does a fourth fundamental element exist?v
Resistor
dv=Rdi
Capacitor
dq=Cdv q i ?
Inductor
dF =Ldi
Memristor
dF =Mdq
Leon Chua proposed the existence of memristor in 1971
In 2008 a team lead by Stanley Williams created the first memristor φ
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4. What is a MEMRISTOR Memristor is really a MEMory ResISTOR
Memristor can be defined as a two
terminal device which shows the
relation between magnetic flux
and charge
memristor symbol
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5. Memristor Theory Or Or
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6. Memristor and Resistor
The way resistor has resistance , memristor has memristance.
Same unit –ohm.
Memristance can be switched to different states.
Memristor has non linear v-i plot.
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7. Memristor features
resistance depends on magnitude, polarity and time application of voltage.
Save its electronic state when current is turned off.
“Remember” how much current has passed through it.
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8. Physical analogy for a memristor
Resistor is analogous to a pipe of fixed diameter through which water is flowing
Water(charge q), input pressure(voltage v), rate of flow of water(current i).
Resitance depends on diameter.
Memristor is analogous to a special kind of pipe that expands or shrinks when water flows through it.
The pipe is directive in nature.
If water pressure is turned off, pipe will retain its most recent diameter, until water is turned back on.
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9. Physical analogy for a memristor
Pipe
Charge
Water
Conductance
Cross sectional area
Potential
Pressure
When water flows in one direction
the diameter increases (resistance decreases)
When water flows in opposite direction
the diameter decreases (resistance increases)
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10. Why memristor a fundamental element Can not be duplicated by R,C,L.
Peculiar behaviour- carries memory of past.
Duplication requires alot of transistors and capacitors.
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11. V-I characteristics Resistor-energy dissipated
Capacitor-store energy in electric field
Inductor-store energy
in magnetic field
MEMRISTOR
Store Information
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12. Course of development
First predicted by Leon Chua in 1971 when he was a rising professor at The university of california.
His paper “Memristor-The missing circuit element”.
was published in the IEEE Transactions on circuit theory.
First solid state version in 2008 by a research team led by R.Stanley Williams of HP Labs.
Reported in a prestigious science journel, NATURE publishes
“The missing memristor found”.
Built from Titanium dioxide with cross bar structure.
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13. Construction of TiO2 memristorPt
TiO2-x
TiO2
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.
Equivalent circuit
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14. Working of TiO2 memristor
Tio2-x
Ron
Roff
Tio2
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15. 1 Working as a switch Positive direction-close the switch.
Off state (high resistance)
On state (low resistance) 1
Positive direction-close the switch.
Negative direction-open the switch.
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16. Memristor structure Crossbar array
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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17. Crossbar array Array of perpendicular wires.
Anywhere two perpendicular
wires cross, there is a switch
connecting them.
To connect any horizontal
wire to a vertical wire the
switch sandwiched between
those two wires must be
closed.
A crossbar array -a storage system.
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18. Types of memristors
1. Molecular and Ionic Thin Film Memristive Systems
Titanium dioxide memristors
Polymeric (ionic) memristors
2. Spin Based and Magnetic memristive systems
Spintronic Memristors/ Spin Torque Transfer (STT)
uses magnetization to alter the spin direction of electrons in two different sections of a device.
magnetization state of the device is changed by current electron spin through spin torque induced magnetization motion.
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19. Materials used Oxides such as WO3,Ir2O3,ZrO2 and RhO2.
Other variations such as TiO ,CuO ,NiO, ZrO.
Perovskite materials.
Molecular and polymer materials- rotaxane
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20. Manufacturing No need of expensive retooling. Nanoimprint lithography.
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22. It’s time to stop shrinking.
A typical processor chip in a laptop contains over a billion transistors.
In which transistors are 1000 times smaller than the diameter of a human hair.
It’s time to stop shrinking.
Further miniaturisation of transistors yields unpredictable results.
The emphasis in electronics design will have to shift to devices that are not just increasingly infinitesimal but increasingly capable.
Memristor is the perfect example of such a device.
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23. Requires a power source to retain a data state.
Transistor
Memristor
3-terminal switching device with an input electrode (e.g. source), an output electrode (e.g. drain), and a control electrode (e.g. gate).
Requires a power source to retain a data state.
Stores data by electron charge.
Scalable by reducing the lateral length and width dimensions between the input and output electrodes.
Capable of performing analog or digital electronic functions depending on applied bias voltages.
Fabrication requires optical lithography.
2-terminal device with one of the electrodes acting either as a control electrode or a source electrode depending on the voltage magnitude.
Does not require a power source to retain a data state.
Stores data by resistance state.
Scalable by reducing the thickness of the memristor materials.
Capable of performing analog or digital electronic functions depending on particular material used for memristor.
Fabrication by potentially cheaper mass production techniques such as nanoimprint lithography.
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24. Benefits Reliability when power is interrupted. Great data density.
Less expensive.
Operating outside of 0s and 1s.
By changing current,behaviour can be changed.
Do not consume power when idle.
May replace transistors in ICs and has the potential to open door to a brand new type of electronics.
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25. Future
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26. Applications As a switch. As a non volatile memory.
Booting free computers.
Can perform logic operations.
In artificial neural networks.
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27. Nonvolatile memories
The resistance-saving property makes memristors very appealing for use in computer memory & freezing property prevents unintentional loss of memory due to a power failure.
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28. Booting free computers
Instant-On Computers
Memristors would potentially be able to remove lengthy reboot since it freezes when power off.
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29. Logic/computing
Memristors appear particularly important to the areas of reconfigurable computing architectures such as FPGAs in which the arrangement between arrays of basic logic gates can be altered by reprogramming the wiring interconnections. Memristors may be ideal to improve the integration density and reconfigurability of such systems.
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30. In artificial neural networks
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31. Synapse=memristor
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32. Hence artificial Brain
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33. Big companies involved in research
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35. Conclusion
The rich hysteretic v-i characteristics detected in many thin film devices can now be understood as memristive behaviour.
It takes a lot of transistors and capacitors to do the job of a single memristor.
No combination of R,L,C circuit could duplicate the memristance.
So the memristor qualifies as a fundamental circuit element.
May replace transistors in Ics and has the potential to open door to a brand new type of electronics.
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36. Conclusion
It is sure that Memristor is going to revolutionaries the 21st century as radically as the transistor in the 20th century
But Memristor will have to wait a few years ,like transistor which had to wait almost a decade after it’s invention for its popular applications.
Finally as Leon O Chua mentioned
It’s time to rewrite all the EE textbooks”
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37. References
"Memristor—The Missing Circuit Element", IEEE Transactions on Circuit Theory by Leon O Chua (1971)
"Memristive Devices and Systems" in the Proceedings of the IEEE by Leon Chua and his student Sung Mo Kang (1976)
"The missing memristor found" Nature (may2008)
IEEE Spectrum - The Mysterious Memristor, by Sally Adee (may 2008)
IEEE Spectrum - How We Found the Missing Memristor, by R. Stanley Williams (dec 2008)
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38. Web links en.wikipedia.org/wiki/Memristor
how-does-a-memristor-work/
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39. Video links
Memristor and Memristive Systems Symposium (4 parts) total of 5 hours
6-Minute Memristor Guide
Memristors The Missing Link(3:38)
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40. THANK
YOU
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