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Memristor is the 4th fundamental element..

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  1. 1. Presented By: Jeevan M. Vas 4SF10EC035
  3. 3. Introduction  Every person with a basic knowledge of electronics would be familiar with the three fundamental circuit elements — RESISTOR CAPACITOR INDUCTOR These three elements are defined by the relation between two of the four fundamental circuit variables — current, voltage, charge and flux.  But, Leon Chua discovered a fourth fundamental circuit element which he named as MEMRISTOR [MEMORY + RESISTOR] 3/27/2014 3Dept. of E & C, SCEM
  4. 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 3/27/2014 4Dept. of E & C, SCEM
  5. 5. Contd..  A Memristor is a semiconductor whose resistance varies as a function of flux and charge. This allows it to “remember” what has passed through the circuit.  Characterized by Memristance. The flux between the two terminals is a function of the amount of electric charge q that has passed through the device . Ø=f(q) 3/27/2014 5Dept. of E & C, SCEM
  6. 6. Features of Memristor • Retain its resistance level even after power had been shut down. • Remember (or recall) the last resistance it had, before being shut off. •“Remember” how much current has pass through it. 3/27/2014 6Dept. of E & C, SCEM
  7. 7. •Microscopic image shows 17 memristors sandwiched between a single bottom wire that makes contact with one side of the device and a top wire that contacts the opposite side. •The devices act as ‘memory resistors’ 3/27/2014 7Dept. of E & C, SCEM
  8. 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). •Resistance depends on diameter. •Memristor is analogous to a special kind of pipe that expands or shrinks when water flows through it. 3/27/2014 8Dept. of E & C, SCEM
  9. 9. •If water pressure is turned off, pipe will retain its most recent diameter, until water is turned back on. 3/27/2014 9Dept. of E & C, SCEM
  10. 10. Memristor Pipe Charge Water Conductance Cross sectional area Potential Pressure When water flows in opposite direction the diameter decreases (resistance increases) When water flows in one direction the diameter increases (resistance decreases) • The pipe is directive in nature. 3/27/2014 10Dept. of E & C, SCEM
  11. 11. Memristor and Resistor •The way resistor has resistance, memristor has memristance. •Same unit -ohm. •Memristor can be switched to different states. •Memristor has non linear V-I plot. 3/27/2014 11Dept. of E & C, SCEM
  12. 12. Current Voltage characteristics of Resistor and Memristor 3/27/2014 12Dept. of E & C, SCEM
  13. 13. Physics of the Device = V(t)=M(q(t))I(t) 3/27/2014 13Dept. of E & C, SCEM
  14. 14. Relation between charge, current, voltage and magnetic flux to one another 3/27/2014 14Dept. of E & C, SCEM
  15. 15. Symmetry of Relationships Memristors Φ=Mq Voltage(V) Current(I) Charge(q) Flux (Φ) Φ = Li v=dΦ/dt i=dq/dt Resistors v=Ri q=Cv 3/27/2014 15Dept. of E & C, SCEM
  16. 16. In 2008 experimental solid state version was reported by R. Stanley Williams of Hewlett Packard (HP) Leon Chua R. Stanley Williams 3/27/2014 16Dept. of E & C, SCEM
  17. 17. Appearance of Memristor Crossbar architecture and magnified memristive switch having platinum electrodes and 2 layers of TiO2 3/27/2014 17Dept. of E & C, SCEM
  18. 18. 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. 3/27/2014 18Dept. of E & C, SCEM
  19. 19. Memristor Operation (a) TiO2-x layer having oxygen deficiencies over insulating TiO2 layer. (b) Positive voltage applied to top layer repels oxygen deficiencies in to the insulating TiO2 layer below. (c) Negative voltage on the switch attracts the positively charged oxygen bubbles pulling them out of the TiO2. 3/27/2014 19Dept. of E & C, SCEM
  20. 20. PT PTTiOv(2-x) TiO2 3 nm 2 nm Oxidized Reduced (-)ve (+)ve • Applied voltage makes the oxygen vacancies (+ve) to shift towards the –ve voltage. Working 3/27/2014 20Dept. of E & C, SCEM
  21. 21. • Shift between the layers is permanent in nature. • It exist even after the voltage has been removed. • Causes the permanent change in resistance. • R(TiO2-x) < R(TiO2) • When w=D, R =RON =Low & when w=0, R=ROFF=High Contd.. 3/27/2014 21Dept. of E & C, SCEM
  22. 22. • No need of expensive retooling. • Nanoimprint lithography. Manufacturing 3/27/2014 22Dept. of E & C, SCEM
  23. 23. 3/27/2014 23Dept. of E & C, SCEM
  24. 24. Applications • As a switch. • As a non volatile memory. • Booting free computers. • Can perform logic operations. • In artificial neural networks. 3/27/2014 24Dept. of E & C, SCEM
  25. 25. Benefits • Would allow for a quicker boot up since information is not lost when the device is turned off. • Hard Disk + RAM = MEMRISTOR. • Uses less energy and produces less heat. • As non-volatile memory, memristors do not consume power when idle. • Density allows for more information to be stored. 3/27/2014 25Dept. of E & C, SCEM
  26. 26. Conclusion • It is sure that Memristor is going to revolutionaries in 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. 3/27/2014 26Dept. of E & C, SCEM
  27. 27. References 1) Memristor resistance modulation for analog applications, Tsung Wen Lee and Janice H Nickel IEEE, electron device letters, vol 33,oct2012. 2) Memristor applications for programmable analog ICs, Sangho Shin and Kyungmin Kim, IEEE transactions on Nanotechnology, vol 10,2011. 3) Compact models for memristor based on charge flux constitutive relationships, IEEE, 2010 IEEE Spectrum: The Mysterious Memristor By Sally Adee. 3/27/2014 27Dept. of E & C, SCEM
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