Memristor symbol

By- Sanjay Soni (2012 2055)

Known Three fundamental passive circuit elements:Resistor, Inductor, Capacitor.

Does a fourth fundamental element exist?v

i

q

φ

Resistordv=Rdi

Capacitordq=Cdv

Inductord=Ldi

Memristord =Mdq

Leon Chua proposed the existence of

memristor in 1971

In 2008 a team lead by

Stanley Williams created the first memristor

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

Memristor Theory

Or

Or

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.

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.

Physical analogy for a memristorMemristor 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)

Why memristor is a fundamental element?

• Can not be duplicated by R,C,L.

• Peculiar behaviour- carries memory of past.

• Duplication requires alot of transistors and capacitors.

V-I characteristics• Resistor-energy

dissipated

• Capacitor-store energy in electric field

• Inductor-store energy

in magnetic field

• MEMRISTOR– Store Information

Construction of TiO2 memristor

TiO2-x TiO2Pt

Equivalent circuit

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.

Working of TiO2 memristor

Tio2-x

Tio2

Ron

Roff

Working as a switch

Off state (high resistance) On state (low resistance)

0 1Positive direction-close the switch.Negative direction-open the switch.

Benefits Reliability when power is interrupted.Great data density. Less expensive.By changing current, behaviour can be changed.Do not consume power when idle. 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. So the circuits by memristors will be more compact.

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Future

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Applications

• As a switch.

• As a non volatile memory.

• Booting free computers.

• Can perform logic operations.

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Nonvolatile memoriesNonvolatile 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.

Conclusion

• No combination of R,L,C circuit could duplicate the memristance.

• It takes a lot of transistors and capacitors to do the job of a single memristor.

• 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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