science

TO-8

TO-8 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 TO-8 rather than just read about it. In short: In electronics, TO-8 is a designation for a standardized metal semiconductor package. TO in TO-8 stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC.

Key takeaways

TO-8 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect TO-8 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TO-8 from memory before moving on to harder problems.

Reference excerpt

In electronics, TO-8 is a designation for a standardized metal semiconductor package. TO in TO-8 stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC. The TO-8 package is noticeably larger than the more common TO-5 package. While originally designed for medium power transistors (that is, higher power than TO-5 but lower than TO-3) such as the 2N1483 series or the AD136, it is more commonly used for integrated circuits and sensors (see Variants below).

Construction

The typical TO-8 metal can package has a base diameter of 15.24 mm (0.600 in), a cap diameter of 12.29 mm (0.484 in), and a cap height of 7.62 mm (0.300 in). The lead diameter is nominally 0.76 mm (0.030 in). The leads are arranged on a circle with a diameter of 7.16 mm (0.282 in). The minimum length of the leads is 10.16 mm (0.400 in).

Variants

Several variants of the original TO-8 package have the same cap dimensions but differ in the number and length of the leads (wires). Somewhat incorrectly, TO-8 is often used in manufacturer's literature as a synonym for any package with the cap dimensions of TO-8, regardless of the number of leads, or even for any package with the diameter of TO-8, regardless of the cap height and the number of leads. Light-sensitive or light-emitting devices have a transparent window, lens, or parabolic reflectors in the top of the case rather than a sealed, flat top. There are variants with between 2 and 16 leads. For packages with more than 4 leads, the leads are usually arranged along the edges of a square with a side length of 10.16 mm (0.400 in) (rather than on a circle as in packages with up to 4 leads or for other metal can packages such as TO-101). These variants usually have a tab to identify lead number 1 and an increased cap diameter of 13.97 mm (0.550 in).

National standards TO-233 is intended to replace previous definitions of TO-8.

References

Illustrations

Worked examples

Example 1 — a first encounter with TO-8

Start with the simplest possible case. Write down what TO-8 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 TO-8 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 TO-8 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 TO-8

In research: TO-8 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 TO-8 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: TO-8 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Semiconductor packages, so understanding it makes those chapters shorter.
In everyday life: Look for TO-8 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 TO-8 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TO-8 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 TO-8 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TO-8 in simple terms?

In electronics, TO-8 is a designation for a standardized metal semiconductor package. TO in TO-8 stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC.

Why does TO-8 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 TO-8?

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 TO-8.