Transistors functions basically as amplifiers, oscillators and switch. It is important to understand transistors codes meanings, how to test their polarity and also how to determine whether it is PNP or NPN type.
In this tutorial we'll be taking further steps into determining the emitter, base and collector of transistors and also how to choose a transistor type for a project.
How to identify NPN and PNP transistors. As we know there are two types of BJTs the NPN and PNP. There are two ways to determine an NPN or PNP transistors.
1. Google searches.
If you don't have a multi-meter or can't use a multi-meter to determine whether a transistor is a NPN or PNP, this is an easy way for you! For example you want to determine what type of junction transistor is 2n2222A you can just search for its by typing spread sheet data of 2n2222A into the search bar and hit search, you will get all information about it pins, codes and current rating.
2.With a multimeter.
This is also a simple method, you don't need to rely on informations on the internet, and this will make you an expert and also give free solutions to people just like I am doing right now. So you gat the knowledge in your head. To test switch the digital multimeter knob to a symbol of diode which is also a continuity tester, take the positive probe and place at the first terminal of the transistor and the negatives pin of the meter to the middle of the transistor, if it displays numbers, therefore it is a PNP. Also take the negative probe to the first terminal of the transistor and the positive probe to the middle if it reads it is an NPN transistor. Transistors codes and meaning. There are many types of transistors out there depending on the maximum current they can withstand, amplification power and even the materials used in constructing them.
1.Codes starting with A or B.
Transistors like BC108 or BC478 made from silicon. Transistors made from silicon are usually marked starting with B. Some transistors starting with A are made from germanium but they are now little used. The letter C indicates low power audio frequency, D means high power audio frequency while F means low power high frequency. The rest of the code identifies the transistor. Sometimes a letter is added to the back of the letter to specify an higher gain version type, for example BC108C, if a circuit specifies an higher gain transistor it must be used for it. But if a circuit specifies a transistor e.g BC108 any type of it can be used.
2.codes starting with TIP.
Some transistors starts with TIP or other names, TIP refers to the company, Texas instruments power transistor while the letter at the back identifes voltage rating specifications. e.g TIP31A.
3.Codes starting with 2N.
Some common transistor's code start with 2N for example 2n2222, 2n3053 etc. It specifies it as an NPN transistor. Sometimes it do have an A at the back eg. 2N2222A. 2N2222A has high current rating than 2N2222.
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Basic Electronics