31-05-2012, 04:13 PM
memristor
memristor .doc (Size: 1.67 MB / Downloads: 46)
INTRODUCTION
After nearly 40 years, researchers have discovered a new type of building block for electronic circuits. And there's at least a chance it will spare you from recharging your phone every other day. Scientists at Hewlett-Packard Laboratories in Palo Alto, California, report in Nature that a new nanometer-scale electric switch "remembers" whether it is on or off after its power is turned off. (A nanometer is one billionth of a meter.)
Researchers believe that the memristor, or memory resistor, might become a useful tool for constructing nonvolatile computer memory, which is not lost when the power goes off, or for keeping the computer industry on pace to satisfy Moore's law, the exponential growth in processing power every 18 months.
You may dimly recall circuit diagrams from your middle school science class; those little boxes with a battery on one end and a light bulb on the other. Ring any bells? Until now, electrical engineers had only three "passive" circuit elements (those that dissipate the energy from a power source) The capacitor accumulates electric charge; the resistor (represented by the light bulb) resists electric current; and the inductor converts current into a magnetic field.
Analogy of Memristor with a Pipe
The classic analogy for a resistor is a pipe through which water (electricity) runs. The width of the pipe is analogous to the resistance of the flow of current--the narrower the pipe, the greater the resistance. Normal resistors have an unchanging pipe size. A memristor, on the other hand, changes with the amount of water that gets pushed through. If you push water through the pipe in one direction, the pipe gets larger (less resistive). If you push the water in the other direction, the pipe gets smaller (more resistive). And the memristor remembers. When the water flow is turned off, the pipe size does not change. Such a mechanism could technically be replicated using transistors and capacitors, but, it takes a lot of transistors and capacitors to do the job of a single memristor.
Consequences of Memristor’s Memory
The memristor's memory has consequences: the reason computers have to be rebooted every time they are turned on is that their logic circuits are incapable of holding their bits after the power is shut off. But because a memristor can remember voltages, a memristor-driven computer would arguably never need a reboot. You could leave all your Word files and spreadsheets open, turn off your computer, and go get a cup of coffee or go on vacation for two weeks. When you come back, you turn on your computer and everything is instantly on the screen exactly the way you left it.
Mathematical Analysis of Its Existence
Leon Chua deduced the existence of memristors from the mathematical relationships between the circuit elements. The four circuit quantities (charge, current, voltage, and magnetic flux) can be related to each other in six ways.
Theory
The memristor is formally defined as a two-terminal element in which the magnetic flux Φm between the terminals is a function of the amount of electric charge q that has passed through the device. Each memristor is characterized by its memristance function describing the charge-dependent rate of change of flux with charge.
Physics behind Memristive Device
This new circuit element shares many of the properties of resistors and shares the same unit of measurement (ohms). However, in contrast to ordinary resistors, in which the resistance is permanently fixed, memristance may be programmed or switched to different resistance states based on the history of the voltage applied to the memristance material. This phenomena can be understood graphically in terms of the relationship between the current flowing through a memristor and the voltage applied across the memristor.
memristor .doc (Size: 1.67 MB / Downloads: 46)
INTRODUCTION
After nearly 40 years, researchers have discovered a new type of building block for electronic circuits. And there's at least a chance it will spare you from recharging your phone every other day. Scientists at Hewlett-Packard Laboratories in Palo Alto, California, report in Nature that a new nanometer-scale electric switch "remembers" whether it is on or off after its power is turned off. (A nanometer is one billionth of a meter.)
Researchers believe that the memristor, or memory resistor, might become a useful tool for constructing nonvolatile computer memory, which is not lost when the power goes off, or for keeping the computer industry on pace to satisfy Moore's law, the exponential growth in processing power every 18 months.
You may dimly recall circuit diagrams from your middle school science class; those little boxes with a battery on one end and a light bulb on the other. Ring any bells? Until now, electrical engineers had only three "passive" circuit elements (those that dissipate the energy from a power source) The capacitor accumulates electric charge; the resistor (represented by the light bulb) resists electric current; and the inductor converts current into a magnetic field.
Analogy of Memristor with a Pipe
The classic analogy for a resistor is a pipe through which water (electricity) runs. The width of the pipe is analogous to the resistance of the flow of current--the narrower the pipe, the greater the resistance. Normal resistors have an unchanging pipe size. A memristor, on the other hand, changes with the amount of water that gets pushed through. If you push water through the pipe in one direction, the pipe gets larger (less resistive). If you push the water in the other direction, the pipe gets smaller (more resistive). And the memristor remembers. When the water flow is turned off, the pipe size does not change. Such a mechanism could technically be replicated using transistors and capacitors, but, it takes a lot of transistors and capacitors to do the job of a single memristor.
Consequences of Memristor’s Memory
The memristor's memory has consequences: the reason computers have to be rebooted every time they are turned on is that their logic circuits are incapable of holding their bits after the power is shut off. But because a memristor can remember voltages, a memristor-driven computer would arguably never need a reboot. You could leave all your Word files and spreadsheets open, turn off your computer, and go get a cup of coffee or go on vacation for two weeks. When you come back, you turn on your computer and everything is instantly on the screen exactly the way you left it.
Mathematical Analysis of Its Existence
Leon Chua deduced the existence of memristors from the mathematical relationships between the circuit elements. The four circuit quantities (charge, current, voltage, and magnetic flux) can be related to each other in six ways.
Theory
The memristor is formally defined as a two-terminal element in which the magnetic flux Φm between the terminals is a function of the amount of electric charge q that has passed through the device. Each memristor is characterized by its memristance function describing the charge-dependent rate of change of flux with charge.
Physics behind Memristive Device
This new circuit element shares many of the properties of resistors and shares the same unit of measurement (ohms). However, in contrast to ordinary resistors, in which the resistance is permanently fixed, memristance may be programmed or switched to different resistance states based on the history of the voltage applied to the memristance material. This phenomena can be understood graphically in terms of the relationship between the current flowing through a memristor and the voltage applied across the memristor.