Put your science elementary books to shredders. Dump all the electrical books in the attic. The researchers at HP have finally proved the existence of fourth basic fundamental building component of any electrical circuit (after resistor, capacitor and inductor) It is the MEMORY RESISTOR or simply called “MEMRISTOR”.
The Memristor was christened by nonlinear-circuit-theory pioneer Leon Chua way back in 1971. So why did it take it so long to prove its existence? Maybe the engineers simply thought the idea is too good to be believed or they were simply ignoring it whenever they encountered it during their experimental sojourns! One of the most probable reasons is that its effect is highlighted only when materials of the size of nanometers are studied. It was HP senior fellow Stanley Williams who stumbled upon the same while working with his team on molecular electronics.
Now how does the Memristor grab the invitation to be at the coveted lunch table with senior members R, L and C? The Memristor is unique in the sense that it “remembers” its past. Sounds weird but true.
The Memristor is passive two terminal device whose resistance depends on the amount of charge that has flowed through the circuit.
In other words if you pass the current in one direction the resistance of Memristor increases.
Now if you supply the current in opposite direction, the resistance will decrease.
And now comes the most interesting thing:
If you switch off the supply, the memristor will have the last value of the resistance (say R1) before it was switched off. If you again switch on supply, memristor will offer the same resistance (R1).
The difference between the Memristor and Varistor is that its resistance depends on the integral of the input applied to the terminals whereas, in Varistors, the resistance depends on the instantaneous value of the input.
Now you may say that the batteries just do the same thing. But Memristor is a passive device unlike active battery and hence makes it distinguishable. Some points to remember:
Memristor has the unit of Memristance (Wb per c, or Ohm) ;
M= døm/ dQ where I= dQ/dt and V= døm/dt.
The Memristor can be thus defined as a two terminal element in which the flux linkage (or integral of voltage) øm, between its terminals is a function of electric charge Q that has passed through the device.
Applications vary from Nonvolatile memory to logic/computation to neuromorphics.
This means that you won’t have to worry about saving all your files before turning off PC in Memristor powered computers. Along with Memristors, scientists have also predicted the existence of memcapacitors and meminductors. Bow down to the new kid on the block!