Sunday, December 19, 2010

Understanding The Mysterious World Of Memristor

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<< Fig shows the concept of HP's memristor circuit a mesh of perpendicular wires known as crossbar arrays; in which memristors are sandwiched between the crossing points. 

You may think what is so special about Memristor?
Hmm... I can give you a reason that it can lead to analog circuits that can think like human brain... :)


The concept of Memristor starts nearly 4 decades ago when in the year 1971 Leon Chua (a professor of electrical engineering at the university of California ) postulated the existence of a fourth fundamental element after examining the relationships between charge and flux in capacitor, inductor and resistor. Till that time for nearly 150 years capacitor, inductor and resistors were considered as the three fundamental passive circuit elements.


 
The 4 element would give the same relationship between charge and flux that is given by a resistor for voltage and current. Such a fundamental element would behave like a resistor whose value would vary according to the current passing through it; but it would be able to remember that value even after the current disappears.

Long since it was theorized no one was able to built it. It became a concept of profound curiosity. But in the year 2008 the researchers of  Hewlett-Packard Stanley Williams and his group revealed that they have discovered the 4th element. "The Memristor". 



         Memresistor crossbar architecture
 
The architecture of Memresistor is a mesh of perpendicular wires known as crossbar arrays; in which memristors are sandwiched between the crossing points.  

Memristor is a two terminal device whose resistance depends upon the magnitude and polarity of the voltage applied to it and the length of the time for which the voltage has been applied. If you  turn off the voltage the memristor is able to remember the recent resistance until the next time you turn it on whether it is the next day or a year later.. That means if you are working on a spreadsheet on your computer, and you turn it off  without closing the documents you will get it as it is the next time you turn on your computer.

This effect can be duplicated by any circuit combination of  resistor, capacitor and inductor that is why the Memristor is termed as the 4th fundamental element.



                     Stanley Williams (left)

You need to boot your computer as the logic circuits do not hold their bits after the power is turned off. But as Memristor is able to remember its history, the wide application of it would be in non-volatile memories. So a computer driven by memristor won't need a reboot. Hence processing time would reduce with much flexibility in computation.

Overall Memristors can be made extremely small and they can be used to make analog circuits working on the same physical principles as a brain. Such a circuit would even lead to machines that can recognize patterns as humans do, real time data analysis for multiple sensors, intelligent physical infrastructure that can provide structural assessment and so on.




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