[LINK] capacitor, resistor, inductor and memristor

[stephen at melbpc.org.au]

http://blog.wired.com/gadgets/2008/04/scientists-prov.html

'Scientists Create First Memristor: Missing Fourth Electronic Circuit 
Element'  By Bryan Gardiner April 30, 2008 | 12:03 PMCategory: Research   

Researchers at HP Labs have built the first working prototypes of an 
important new electronic component ..

The new component is called a memristor, or memory resistor. 

Up until today, the circuit element had only been described in a series of 
mathematical equations written by Leon Chua, who in 1971 was an 
engineering student studying non-linear circuits. 

Chua knew the circuit element should exist -- he even accurately outlined 
its properties and how it would work. Unfortunately, neither he nor the 
rest of the engineering community could come up with a physical 
manifestation that matched his mathematical expression.

Thirty-seven years later, a group of scientists from HP Labs has finally 
built real working memristors, thus adding a fourth basic circuit element 
to electrical circuit theory, one that will join the three better-known 
ones: the capacitor, resistor and the inductor. 

Researchers believe the discovery will pave the way for instant-on PCs, 
more energy-efficient computers, and new analog computers that can process 
and associate information in a manner similar to that of the human brain.

According to R. Stanley Williams, one of four researchers at HP Labs' 
Information and Quantum Systems Lab who made the discovery, the most 
interesting characteristic of a memristor device is that it remembers the 
amount of charge that flows through it.

Indeed, Chua's original idea was that the resistance of a memristor would 
depend upon how much charge has gone through the device. In other words, 
you can flow the charge in one direction and the resistance will increase. 
If you push the charge in the opposite direction it will decrease. Put 
simply, the resistance of the devices at any point in time is a function 
of history of the device –- or how much charge went through it either 
forwards or backwards. That simple idea, now that it has been proven, will 
have profound effect on computing and computer science.

"Part of what's going to come out of this is something none of us can 
imagine yet," says Williams. "But what we can imagine in and of itself is 
actually pretty cool."

For one thing, Williams says these memristors can be used as either 
digital switches or to build a new breed of analog devices.

For the former, Williams says scientists can now think about fabricating a 
new type of non-volatile random access memory (RAM) – or memory chips that 
don't forget what power state they were in when a computer is shut off.

That's the big problem with DRAM today, he says. "When you turn the power 
off on your PC, the DRAM forgets what was there. So the next time you turn 
the power on you've got to sit there and wait while all of this stuff that 
you need to run your computer is loaded into the DRAM from the hard disk."

With non-volatile RAM, that process would be instantaneous and your PC 
would be in the same state as when you turned it off.

Scientists also envision building other types of circuits in which the 
memristor would be used as an analog device.

Indeed, Leon himself noted the similarity between his own predictions of 
the properties for a memristor and what was then known about synapses in 
the brain. One of his suggestions was that you could perhaps do some type 
of neuronal computing using memristors. HP Labs thinks that's actually a 
very good idea. 

"Building an analog computer in which you don't use 1s and 0s and instead 
use essentially all shades of gray in between is one of the things we're 
already working on," says Williams. These computers could do the types of 
things that digital computers aren't very good at –- like making 
decisions, determining that one thing is larger than another, or even 
learning.

While a lot of researchers are currently trying to write a computer code 
that simulates brain function on a standard machine, they have to use a 
huge machines with enormous processing power to simulate only tiny 
portions of the brain.

Williams and his team say they can now take a different approach: "Instead 
of writing a computer program to simulate a brain or simulate some brain 
function, we're actually looking to build some hardware based upon 
memristors that emulates brain-like functions," says Williams.

Such hardware could be used to improve things like facial recognition 
technology, and enable an appliance to essentially learn from experience, 
he says. In principle, this should also be thousands or millions of times 
more efficient than running a program on a digital computer.

The results of HP Labs teams findings will be published in a paper in 
today's edition of Nature. As far as when we might see memristors actually 
being used in actual commercial devices, Williams says the limitations are 
more business oriented than technological.

Ultimately, the problem is going to be related to the time and effort 
involved in designing a memristor circuit, he says. 

"The money invested in circuit design is actually much larger than 
building fabs. In fact, you can use any fab to make these things right 
now, but somebody also has to design the circuits and there's currently no 
memristor model. 

The key is going to be getting the necessary tools out into the community 
and finding a niche application for memristors. How long this will take is 
more of a business decision than a technological one."

--
Cheers Mark
Stephen Loosley
Victoria, Australia