Memristor as the name suggest is a type of resistor with a memory. In other words a memristor is a device that keeps record of the current passing through it. Memristors are basically the passive circuit elements, and has been regarded as fourth class of electrical circuit following the resistor, the capacitor, and the inductor in the hierarchy.
The concept of memristor was put forward by Leon Chua, a circuit theorist, in 1971. He considered the memristor to be related as the link between charge and magnetic flux, just as resistor relates voltage and current, capacitor relates voltage and charge, and inductor relates flux and current. Thereafter the potential of a memristor device was envisaged and various companies started working on creating a practical memristor from the theory forwarded by Leon Chua.
In 2008, Hewlett-Packard, developed a switching memristor, made of a thin film of titanium oxide. Thereafter the series of developments took placements so as to commercialize the use of memristor in the development of electronic devices.
Just like the resistor possess resistance, capacitor possess capacitance, inductor possess inductance, and so memristor possess memristance. The memristance is denoted by M and is given by
where dphi is the change in magnetic flux and dq is the change in the charge. Here M(q) is denoted as a function of charge. Since magnetic flux is the integral of voltage and charge is the integral of current. So we have
In other words the memristance is the slope of the functional relationship between the time integral of current i.e charge and the time integral of voltage i.e flux.
The unit of memristance is given by weber/coulomb or ohm.
Since the development of memristor is still under procees, there are no data sheets available for this element. So the properties of memristor can be studied under the Hysterisis curve.
Memristor is a dynamic circuit element which has the potential to revolutionize the present trend of the electrical and electronics industries. The major potential applications of a memristor are as below.
- Replacing transistors- The memristors would be good substitutes of transistors. This is dedicated to their much smaller size, since the domains of memristors are being studied and developed under the nanoscales. But this potential substitution requires huge investment, since the transistor is still the cheapest in regard to the memristor, though the latter have some quality advantages over the former.
- Extending the notion of memristors- The notion of the memristors can be applied to the other elements. For eg- memcapacitors i.e memory capacitors and meminductors for memory inductors. This would provide a variety of memory storage elements that can be used under the diverse field applications. Also with the studies related to the memristors, it would be easier to study the other potential memory elements discussed above.
- Memory applications- Now since it is a dynamic memory element. So it must be having some applications in relation to the memory devices. The use of memristors would allow greater data density than hard drives, with fast access time. Even it has the potential to replace DRAMs with access times of about one tenth of the latter. In addition to this, the ability of memristors to retain memory in the power off states can change the present state of RAMs which loose data when the power is off.