1. Seminar Presentation on
MEMRISTOR
“The Fourth Basic Circuit Element”
By-
Helal Uddin Mullah
Mtech 2nd Semester
MTV/EC13/05
mullahz251@gmail.com

2. Contents
 What is Memristor?
 History
 Theory
 Construction & Working
 An analogy
 Properties
 Applications
 Advantages
 Conclusion
 References
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3. WHAT IS MEMRISTOR?
• A memristor is a semiconductor whose resistance varies as a function of flux and
current. This allows it to “remember” what has passed through the circuit.
• It is the fourth fundamental circuit element.
• Two terminal device.
• Its resistance depends on the amount of
charge passed through it.
• That’s why it is called “memristor”(memory resistor).
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Memristor

4. Memristance
• Memristance is simply charge-dependent resistance.
• Unit - ohm (Ω)
• Symbol
V(t) = M(q(t))*I(t)

5. Emergence Of Memristic Theory
• Theory was developed in 1971 by
Professor Leon Chua at University of
California, Berkeley.
• Found while exploring symmetry
between the three fundamental passive
linear circuit elements.
• In 2006, R.Stanley Williams developed
practical model.

7. Three Fundamental Circuit Elements
Resistor
v R i 
Capacitor
q C v 
Inductor
L i  
Resistor
Georg Ohm 1827
Capacitor
von Kleist 1745
Inductor
Michael Faraday 1831

8. Symmetry Of Relationships
Memristors
Φ=Mq
Voltage
(V)
Current(i)
Charge (q) Flux (Φ)
Φ = Li Inductors
v=dΦ/dt i=dq/dt
Resistors
v=Ri
q=CvCapacitors

9. Theory
Or
Or
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10. Working of TiO2 Based Memristor
Pt TiTiOv(2-x)
TiO2
3 nm
2 nm
dopeddepleted
(-)ve (+)ve
 The HP device is composed of a thin (50 nm) titanium dioxide film between two
5 nm thick electrodes, one Ti, the other Pt. Initially, there are two layers to the
titanium dioxide film, one of which has a slight doped of oxygen atoms.
 The oxygen vacancies act as charge carriers, meaning that the doped layer has a
much lower resistance than the non- depleted layer.
 When an electric field is applied, the oxygen vacancies drift ,changing the boundary
between the high-resistance and low-resistance layers.

11.  Thus the resistance of the film as a whole is dependent on how much charge has
been passed through it in a particular direction, which is reversible by changing the
direction of current.
Memristance is displayed only when both the
doped and depleted layers contribute to resistance.
 At a point of time, when enough charge will flow
in the film, no ion will be moving then the device enters
in to saturation and gives a constant value of M(q)
and remains fixed until we reverse the direction of
current flow.
In this TiO2 Memristor model, for RON<<ROFF
The memristance is
Where
μv = mobility of dopant
D= thickness of the film.
Equivalent Circuit.

12. • Retain its resistance level even after power had
been shut down.
• Remember (or recall) the last resistance it had,
before being shut off.
• By changing the speed and strength of the
current, it is possible to change the behavior of
the device.
• A fast and hard current causes it to act as a
digital device.
• A soft and slow current causes it to act as an
analog device.
Property Of Memristor

13. Applications
 As a switch
 As a non volatile memory
 Can perform logic operations
 In artificial neural networks
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1 cm3 of memristor = 1 terabit

14. Benefits Of Memristor Technology
• Would allow for a quicker boot up since information is not lost when the device is
turned off.
• Uses less power and produces less heat.
• Eliminates the need to write computer programs that replicate small parts of the
brain.
• Density allows for more information to be stored.
• Provides greater resiliency and reliability when power is interrupted in data centers.
• Creating a Analog Computer that works much faster than Digital ones.
• Conventional devices use only 0 and 1; Memristor can use anything between 0 and
1.
• Faster than Flash memory.
Allow digital cameras to take pictures with no delay in between.
• Compatible with current CMOS interfaces.

15. Not Perfect Yet !
• Though hundreds of thousands of memristor
semiconductors have already been built, there is still
much more to be perfected.
• Needs more defect engineering.
• No design standards (rules).

16. Conclusion
 In April 2010, HP labs announced that they had practical memristors working at
1 ns (~1 GHz) switching times and 3 nm by 3 nm sizes, which bodes well for
the future of the technology.At these densities it could easily rival the current
sub-25 nm flash memory technology.
 So,it is sure that Memristor will change circuit design in the 21st century as radically
as the transistor changed it in the 20th.
 As scientist are saying that Moore’s law is going to be saturated by 2022, we will now
have memristors as alternative to transistors.
 Finally as Leon O Chua mentioned “It’s time to rewrite all the EE textbooks”

17. References
• L. O. Chua, “Memristor-the missing circuit element,” IEEE Trans. Circuit Theory,
vol. 18,pp. 507 -519, Sep. 1971.
• D. B. Strukov, G. S. Snider, D. R. Stewart, and R. S. Williams, “The missing
memristor found.," Nature, vol. 453, no. 7191, pp. 80 -83, 2008.
• M. Di Ventra, Yu. V. Pershin, L. O. Chua, “Circuit elements with memory:
memristors, memcapacitors and meminductors”. 2009. arXiv:0901.3682.
• L. O. Chua, “Resistance switching memories are memristors," Appl. Phys. A, vol.
102,pp. 765-783, 2011.
• http://en.wikipedia.org/wiki/Memristor
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