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Field-effect transistor

Field-effect transistor is a 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 Field-effect transistor rather than just read about it. In short: The field-effect transistor (FET) is a type of transistor that uses an electric field to control the current through a semiconductor. It comes in two types: junction FET (JFET) and metal–oxide–semiconductor FET (MOSFET).

Field-effect transistor — main illustration
Field-effect transistor — illustration

Key takeaways

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

Reference excerpt

The field-effect transistor (FET) is a type of transistor that uses an electric field to control the current through a semiconductor. It comes in two types: junction FET (JFET) and metal–oxide–semiconductor FET (MOSFET). FETs have three terminals: source, gate, and drain. FETs control the current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and source. FETs are also known as unipolar transistors since they involve single-carrier-type operation. That is, FETs use either electrons (n-channel) or holes (p-channel) as charge carriers in their operation, but not both. Many different types of field-effect transistors exist. Field effect transistors generally display very high input impedance at low frequencies. The most widely used field-effect transistor is the MOSFET.

History

… excerpt ends here. Continue reading the full article.

Illustrations

Field-effect transistor: Cross-sectional view of a MOSFET type field-effect transistor, showing source, gate and drain terminals, and insulating oxide layer.
Cross-sectional view of a MOSFET type field-effect transistor, showing source, gate and drain terminals, and insulating oxide layer.
Field-effect transistor: Julius Edgar Lilienfeld, who proposed the concept of a field-effect transistor in 1925.
Julius Edgar Lilienfeld, who proposed the concept of a field-effect transistor in 1925.
Field-effect transistor: Cross section of an n-type MOSFET
Cross section of an n-type MOSFET
Field-effect transistor: I–V characteristics and output plot of a JFET n-channel transistor
I–V characteristics and output plot of a JFET n-channel transistor
Field-effect transistor: Simulation result for right side: formation of inversion channel (electron density) and left side: current-gate voltage curve (transfer characteristics) in an n-channel nanowire MOSFET. Note that the threshold voltage for this device lies around 0.45 V.
Simulation result for right side: formation of inversion channel (electron density) and left side: current-gate voltage curve (transfer characteristics) in an n-channel nanowire MOSFET. Note that the threshold voltage for this device lies around 0.45 V.

Worked examples

Example 1 — a first encounter with Field-effect transistor

Start with the simplest possible case. Write down what Field-effect transistor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In 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 Field-effect transistor 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 Field-effect transistor 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 Field-effect transistor

In research
Field-effect transistor appears in 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 Field-effect transistor 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
Field-effect transistor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arab inventions, Austrian inventions, Egyptian inventions, so understanding it makes those chapters shorter.
In everyday life
Look for Field-effect transistor 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.

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How to study Field-effect transistor in 20 minutes

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

Frequently asked questions

What is Field-effect transistor in simple terms?

The field-effect transistor (FET) is a type of transistor that uses an electric field to control the current through a semiconductor. It comes in two types: junction FET (JFET) and metal–oxide–semiconductor FET (MOSFET).

Why does Field-effect transistor matter?

Because it connects several 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 Field-effect transistor?

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 Field-effect transistor.

Tags

  • Arab inventions
  • Austrian inventions
  • Egyptian inventions
  • Field-effect transistors
  • Hungarian inventions
  • Japanese inventions
  • South Korean inventions
  • Transistor types

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