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What is a PCB Transistor and How Can You Test it?

Before you can comprehend how a PCB transistor functions, you must first understand what a transistor is and what to check for when choosing one. Before you purchase a PCB transistor, you must learn how you should test one.

What is a PCB Transistor?

Transistors are electronic devices that regulate the flow of electrons and hence regulate electricity. It implies they are in charge of initiating and terminating the electric current flow. Its main function is switching as well as enhancing the quantity of electronic impulses passing via circuit boards.

PCB Transistor Types

PNP and NPN are the two distinct kinds of transistors, and each has a different circuit symbol. Each of both transistors, which are built of semiconductor materials, has a unique set of layers. NPN silicon transistors, which are the simplest to produce, are the most widely used transistors.

Any novice must always begin by understanding NPN since they’re the simplest to comprehend. If you comprehend the NPN, it’ll be simple to help you study the full transistor and its various varieties.

How to Read PCB Transistors

transistor Component

NPN and PNP are the two most prevalent varieties of transistors, yet all of them can be made in many ways and are unique. Learning about transistors and understanding how to interpret a PCB transistor are the initial steps. Once you have mastered reading, then the next step for you is learning ways of testing them.

Our article would explain and teach you through the process involved in the reading a PCB transistor.

It is crucial to test the transistors so you can determine whether they will be helpful or not. Start by locating the marking beneath or close to the transistor.

  • Search for a line, an arrow, or a triangle with sides as well as a line beneath that appears to link them.
  • Unless the PCB transistor lacks that line, use that line which comes out from the left like the base. The metal enclosure acts as a foundation in the event that such a line is absent.
  • The transistor should be positioned so that the line that comes out faces the left hand side.
  • Be sure to locate and highlight the triangle since this NPN collector would be pointed upward and your PNP collector would be pointing below.

Testing the PCB Transistor


In circuits, transistors play a crucial role, thus it’s crucial to make sure they’re functional. When they are flawed, the circuit fails as a result. Because of this, it is crucial that you test them in order to make sure they are operating as intended. Be sure you understand what is expected of you before you start the procedure. A step-by-step tutorial for testing a PCB transistor is provided here.

Step 1

Before testing your transistor, make sure that there’s no electricity flowing through the circuit by ensuring it is switched off.

The battery should then be removed after unplugging its AVC power connection. Make sure that there’s no power present on the circuit board before simultaneously touching a capacitor’s two terminals with any metal. To prevent turning off stored power, use the screwdriver with insulation at the handle end.

Step 2

Watch out for the transistor that you will be testing for its collector, base, as well as emitter leads. These leads on some transistors are labeled for simple identification. C B, E, and B will be imprinted on them. By being certain of the orientation of leads, you should request a catalog from your electronics supplier. You should have confidence because the placements of the points vary depending on the transistor.

Step 3

If your digital multimeter has the diode setting, use it in this step; if not, use ohms setting. If the transistor is operating in the analog environment, set it using a low ohm scale.

Step 4

Touch a lead from of the meter into a base lead whilst you place its other on your collector lead to check the reading of the collector in both base-collector directions. Review the reading then share your advice. The transistor would display a reading for one direction as well as infinity for the other if it is functioning properly.

Step 5

While touching a lead towards the base while the other connects to an emitter, you must check the reading of the emitter on its base in the two directions.

Reverse these leads to read the meter in an opposite direction after checking it. Similar to step four, anticipate one reading should display 600 while the other will show an unlimited number.

Step 6

PCB Transistor
PCB Transistor

Remove its base lead if the reading isn’t really near to 600 because other components might be affecting the reading. Disconnect the data from the PCB by melting its solder attaching its base lead onto it. Using the meter, check both routes from of the base towards the collector-base towards the emitter. When you’re done taking the reading for the meter, melt your solder, push this lead into the hole of the board, and then reinstall it.

Step 7

Here comes the last step. Following testing, you ought to be able to tell if the collector or base-emitter readings indicate 0 in the two directions or if both indicate endless tasks. Zeros indicate a brief period of time. Moreover, infinities are signs of the open transistor diode.

However you are welcome to look here if you’d like to know more regarding how to thoroughly inspect a circuit board.


Prior to making a purchase of a PCB transistor, you must be aware of the transistor that you intend to utilize. In order to ensure that you’re getting the best open that suits you out of the many variations on the market, you must take care of a few things. The majority of providers will classify transistors based on their intended usage or the power rating.

In addition, if you don’t know much or are unfamiliar with pcb transistors, then it is crucial to speak with a professional to avoid making a mistake.




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