computer science

Memistor

Memistor is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Memistor rather than just read about it. In short: A memistor is a nanoelectric circuitry element used in parallel computing memory technology. Essentially, a resistor with memory able to perform logic operations and store information, it is a three-terminal implementation of the memristor.

Key takeaways

Memistor belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Memistor to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Memistor from memory before moving on to harder problems.

Reference excerpt

A memistor is a nanoelectric circuitry element used in parallel computing memory technology. Essentially, a resistor with memory able to perform logic operations and store information, it is a three-terminal implementation of the memristor.

History While the memristor is defined in terms of a two-terminal circuit element, there was an implementation of a three-terminal device called a memistor developed by Bernard Widrow in 1960. Memistors formed basic components of a neural network architecture called ADALINE developed by Widrow. The memistor was also used in MADALINE.

Essence In one of the technical reports the memistor was described as follows:

Like the transistor, the memistor is a 3-terminal element. The conductance between two of the terminals is controlled by the time integral of the current in the third, rather than its instantaneous value as in the transistor. Reproducible elements have been made which are continuously variable (thousands of possible analog storage levels), and which typically vary in resistance from 100 ohms to 1 ohm, and cover this range in about 10 seconds with several milliamperes of plating current. Adaptation is accomplished by direct current while sensing the neuron logical structure is accomplished nondestructively by passing alternating currents through the arrays of memistor cells. Since the conductance was described as being controlled by the time integral of current as in Chua's theory of the memristor, the memistor of Widrow may be considered as a form of memristor having three instead of two terminals. However, one of the main limitations of Widrow's memistors was that they were made from an electroplating cell rather than as a solid-state circuit element. Solid-state circuit elements were required to achieve the scalability of the integrated circuit which was gaining popularity around the same time as the invention of Widrow's memistor. An article on ArXiv suggests that the floating-gate MOSFET as well as other 3-terminal "memory transistors" may be modeled using dynamical systems equations in a similar fashion to the memristive systems of memristors.

Illustrations

Worked examples

Example 1 — a first encounter with Memistor

Start with the simplest possible case. Write down what Memistor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Memistor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Memistor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Memistor

In research: Memistor appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Memistor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Memistor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Electrical components, Electronic circuits in computer storage, so understanding it makes those chapters shorter.
In everyday life: Look for Memistor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Memistor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Memistor means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Memistor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Memistor in simple terms?

Why does Memistor matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Memistor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Memistor.