History

Although the memristor

Memristor

Memristor is a passive two-terminal electrical component envisioned by Leon Chua as a fundamental non-linear circuit element relating charge and magnetic flux linkage...

 is defined in terms of a 2-terminal circuit element, there was an implementation of a 3-terminal device called a memistor developed by Bernard Widrow

Bernard Widrow

Bernard Widrow is a U.S. professor of electrical engineering at Stanford University. He is the co-inventor of the Widrow–Hoff least mean squares filter adaptive algorithm with his then doctoral student Ted Hoff...

 in 1960. Memistors formed basic components of a neural network architecture called ADALINE

ADALINE

ADALINE is a single layer neural network. It was developed by Professor Bernard Widrow and his graduate student Ted Hoff at Stanford University in 1960. It is based on the McCulloch–Pitts neuron...

 developed by Widrow and Ted Hoff (who later invented the microprocessor at Intel).

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

Integrated circuit

An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

 which was gaining popularity around the same time as the invention of Widrow's memistor.

A Google Knol

Knol

Knol is a Google project that aims to include user-written articles on a range of topics. The project was led by Udi Manber of Google, announced December 13, 2007, and was opened in beta to the public on July 23, 2008 with a few hundred articles mostly in the health and medical field.Knol has no...

 article suggests that the Floating Gate MOSFET

Floating Gate MOSFET

The Floating Gate MOSFET is a field effect transistor, whose structure is similar to a conventional MOSFET. The gate of the FGMOS is electrically isolated, creating a floating node in DC, and a number of secondary gates or inputs are deposited above the floating gate and are electrically isolated...

as well as other 3-terminal "memory transistors" may be modeled using memristive systems equations.