Discrete Semiconductor Kit Identification Guide

Contributors: Byron J.
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Kit Contents

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Spilled Onto The Workbench

List of contents

You will find the following parts in the kit.

Discrete Semiconductor Kit Bill Of Materials
Quantity Part Number
& Link toDatasheet
Type Marking
25 2N3904 NPN Transistor 2N3904
25 2N3906 PNP Transistor 2N3906
10 5LN01SP N-channel MOSFET YB
10 5LP01SP P-Channel MOSFET XB
20 1N4148 Silicon Diode 4148
20 1N4004 Power Diode 1n4004
5 TL431A Voltage Reference TL431A
5 LM317L Voltage Regulator LM317LZ

A lot of these parts look very similar. The “marking” column above indicates the designation that you’ll find printed in the part itself. With the exception of the MOSFETs, the marking usually contains a version of the part number. Some parts may also have additional symbols or printing, indicating things like the manufacturer and date of production.

The BJTs, voltage references and regulators are all the common TO-92 form factor, with a body about the size of a pencil eraser, and three protruding legs. The MOSFETs are the slightly smaller SC-72 (AKA “Single SPA”) package.

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Comparison of TO-92 and SC-72 Packages

The polarity of these devices is important, and usually referenced by pin number.

To identify the pins, hold the device so that the marking side is factng you, and the legs are pointing downwards. From left to right, the pins are numbered 1, 2 and 3. The function assigned to each pin depends on the device, and we’ll cover that for each part in its respective section.

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TO-92 Pin Numbering


Because discrete semiconductors are a basic building block of electronic circuits, they have much more detailed specifications than other components. A critical parameter in one application might be nonsensical in another. This makes it hard to present an abbreviated synopsis of part specs. Rather than listing some parameters inline, we’ve instead decided to make it easy to access the parametric information, by linking the part numbers in the table above table to the corresponding datasheets.