Memristor, as its name indicates, is closely related to memory. Memristor is a circuit element that remembers how much current or charge has been passed through it. Behavior of memristor depends upon the history of the device - meaning how much current/charge went through it in the previous cycle etc. Additionally by alternating the current that pass through it, memristor can become one element circuit component with unique properties. Because memristor can save its state even if the supply of current is turned off, it becomes an ideal replacement for flash memories, ROM and RAM chips of today. Theoretically memristor is cheaper and faster when compared to flash.

The memristic theory was developed in 1971 by Professor Leon Chua, then engineering student studying non-linear circuits. He accurately described the device properties and characteristics but it took almost four decades to develop the first prototype of memristor. Researchers at HP Labs are the first ones to produce a prototype of memristor and thanks to them that now we have four basic circuit elements instead of conventional three - Resistor, Capacitor, Inductor and Memristor.

Resistor	Capacitor
Inductor	Memristor

Basic Attributes of Memristor:

1. It works like a charge dependence resistance.
2. The unit of memristor is Ohm.
3. It consume less energy and generate less heat making it ideal possible replacement for flash.
4. It offers better reliability and resiliency in case of power interruption.
5. No power consumption in idle state and is compatible with CMOS interfaces.
6. High packing density allows more storage at low cost.

Types of Memrsitors

Broadly there are two-types of memristor, each type is having further sub categories in it

1. Ionic Thin Film and Molecular Memristors: These memristors mostly are dependent on distinct material attributes or physical properties of thin film atomic lattices that show hysteresis under the application of the charge. These are further divided as follows:
• Titanium Dioxide Memristors
• Ionic or polymeric Memristors
• Resonant Tunnening Diode Memristors
• Manganite Memristors
2. Magnetic and Spin based Memristors: They work totally different from thin film or molecular memristor. They are not based on physical properties but they are dependent upon property of degree of freedom in electron rotation or spin for hysteresis like phenomena to occur. It is further classified as follows:
• Spintronic Memristors
• Spin Torque Transfer Memristors

Since the memristors are theoretically faster, non-volatile (memory), have low power consumption, generate less heat and offer high packing density they are ideal choice for making faster computers in future. Memristors find applications in logic circuits design, digital memory design, and neuromorphic systems because they work like biological synapses

By - Monica, Assistant Prof, CSE, Chitkara University, HP

References:-

1. https://link.springer.com
2. http://ieeexplore.ieee.org/abstract/document
3. http://www.worldscientific.com