The Field-effect transistor: Types And Terminals

The Field-effect transistor Types And Terminals
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You must have often heard this name Field-effect transistor, electric field people know it by its short-form FET. But do you exactly what it is and for what it is used? I know most of you do not know about it, Although many of you have heard this name many times before, but still you never paid attention to it. So in this article, we will know about Field-effect transistor, what it is and its usage.

What is Field-effect transistor

The field-effect transistor which is known as FET is an electronic device which uses an electric field to control the flow of current. Like many other transistors, the field-effect transistor has also three terminals which are called ‘source’, ‘drain’ and ‘gate’. FETs control the flow of current by the application of a voltage to the gate and applying a threshold voltage to the gate allows a current to flow from the source to the drain. The FET can be used as a switch by increasing and decreasing the gate voltage around its threshold value. By increasing the gate voltage above the threshold, Field Effect Transistor operate as current amplifiers.

There is another name by which field-effect transistor is known, and that is “Unipolar Transistor.” And the reason why it is known as Unipolar Transistor because they involve single-carrier-type operation. That is, FETs use holes or electrons as charge carriers in their operation, but not both.

The Beginning Of Field Effect Transistor

It was 1925 when the first time the concept of a FET patented and the Austro Hungarian physicist Julius Edgar Lillenfeld is the man who was behind it. Also, there was another man Pakar Heal, who did this in 1934. But unfortunately, both of them were unable to build a working practical semiconducting device based on their concept.

After the 17-year patent expired, in 1947, the transistor was observed and explained by William Schockley’s team at Bell Laboratories. Shockley initially attempted to build a working FET by trying to modulate the conductivity of a semiconductor but was also unsuccessful. The first FET device to be successfully built was the Junction Field-Effect Transistor (JFET) which was first patented in 1945 by Heinrich Welker. In 1950, two Japanese engineers Jun-ichi Nishizawa and Y. Watanabe invented a new type of JEFT, which known as the static induction transistor (SIT). In 1953 two engineers George F. Dacey and Ian M. Ross were built a working practical JFET and the special thing about this invention is that they built it by following Shockley’s theoretical treatment.

Although JFET was a very useful tool, it still had issues, and in the process to repair these issues many other variants of the FETs were invented. In 1959 there was a major change came in the field of a FETs, and that change was the discovery of MOSFET i.e. metal – oxide – semiconductor field-effect transistor. The metal–oxide–semiconductor field-effect transistor (MOSFET) was invented by Mohamed Atalla and Dawon Kahng.

After that in the field of field-effect transistor many other things also invented, such as CMOS (complementary MOS) by Chih-Tang Sah and Frank Wanlass at Fairchild Semiconductor in 1963, the first report of a floating-gate MOSFET by Dawon Kahng and Simon Sze in 1967 and a double-gate MOSFET was first demonstrated in 1984 by Electrotechnical Laboratory researchers Toshihiro Sekigawa and Yutaka Hayashi.

Terminals of Field Effect Transistor

As I mentioned above there are three terminals of field-effect transistor, Source, Drain, and Gate, so let’s take a short instruction of them…

  1. Source – Source (S), is the terminal through which the carriers enter the channel and traditionally, current entering the channel at S is designated by IS.
  2. Drain – Drain (D), is the terminal through which the carriers leave the channel and traditionally, current entering the channel at D is designated by ID and Drain-to-source voltage is VDS.
  3. Gate – Gate (G) is the terminal that modulates the channel conductivity and by applying voltage to G, one can control ID.

Types Of Field Effect transistors

Although I mentioned about some type or subtype of Field-effect transistors above still there are so many other. Field-effect transistors have total 16 types, so here are the names…

The MOSFET (metal-oxide-semiconductor field-effect transistor)

The JFET (junction FETs)

The MNOS (metal–nitride–oxide–semiconductor transistor)


The FREDFET (fast-reverse or fast-recovery epitaxial diode)

The HIGFET (heterostructure insulated-gate FET)

The MODFET (modulation-doped field-effect transistor)

The TFET (tunnel FETs)

The HEMT (high-electron-mobility transistor)

The ISFET (ion-sensitive FETs)

The BioFET (Biologically sensitive field-effect transistor)

The MESFET (metal-semiconductor FETs)


The GNRFET (graphene nanoribbon FETs)

The VeSFET (vertical-slit field-effect transistor)

The CNTFET (carbon nanotube FETs)

The OFET (organic FETs)

The DNAFET (DNA field-effect transistor)

The QFET (quantum FETs)

The SB-FET (Schottky-barrier field-effect transistor)


The Fe FET

So these are the types of FETs that are more than 20. At present, A MOSFET (metal-oxide-semiconductor field-effect transistor) is the fundamental transistor behind most of the electronics including computers. MOSFET has a metal contact for the gate and it is separated from the bulk transistor (substrate) by an oxide layer, typically SiO2 (silicon dioxide) which makes sure no current flows through the gate.

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So this is the basic knowledge of field-effect transistor, in future, we will learn more about it such as the how field-effect transistor works and its advantages and disadvantages. Hopefully, today’s our article will prove useful to you but still if you have any questions or concerns about FETs you can ask us in the comments section.


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