Finding the base, collector, and emitter of an electronic transistor using a multimeter.

Steemian Friends,
Today, I will discuss a transistor for electronics work. Although a transistor is a small electronic device, its function and importance are very high. Below, I will show the structure of a transistor and its measurement with a multimeter.

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Transistors act as switching devices in electronic circuits. There are two types of transistors. Transistors are made of P-type and N-type semiconductors.

• PNP transistor
• NPN transistor

NPN Transistor Structure

I have shown the structure of a transistor in the picture below. PNP transistor is made of two P-type and one N-type semiconductor. On the other hand, the NPN transistor is composed of two N-type and one P-type semiconductor, as shown in the picture.

PNP Transistor Structure

A transistor has three terminals.

• Base
• Collector
• Emitter

Now, I will show you how to determine the base, collector, and emitter of a transistor using a multimeter. The terminals of a transistor are not marked. To be skilled in electronics, one must know how to identify the terminals of a transistor.

Step 01:

I create a small gap between the three terminals of a transistor, as shown in the figure below. Then, I mark the three terminals on paper as 1, 2 and 3. Then, I set the multimeter's selector switch to the ohms range. I have shown it in the picture.

A transistor and multimeter setup in the ohms range

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Step 02:

Then, I hold the black knob of the multimeter to the number one terminal of the transistor. Then I hold the red knob of the multimeter to the number two and three terminals. I do not see ohms on the multimeter. I have shown it in the picture below.

Check with a multimeter by holding the first terminal of the transistor to the common terminal.

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Step 03:

Then, I hold the black knob of the multimeter to the number two terminal of the transistor. I have the red knob of the multimeter to the number one and three terminals. This time, I still do not see ohms on the multimeter. It is shown in the picture below.

Check with a multimeter by holding the second terminal of the transistor at the common point.

Step 04:

Then, I hold the black knob of the multimeter to the number three terminal of the transistor. Now I have the red knob of the multimeter to the number one and two terminals of the transistor. Now I see two ohms on the multimeter. I measure 10.64 ohms on the first terminal of the transistor and 9.30 ohms on the second terminal.

Check with a multimeter by holding the third terminal of the transistor common.

Result:

• I tested in the fourth step and found an ohm reading at terminals 1 and 2. Since the third terminal is the common terminal, it is the base of the transistor.

Finally, the base, collector and emitter are identified.

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• The number one end has more ohms, so it is the Emitter. The end with higher ohms is the Emitter.

• The resistance was low at terminal number two of the transistor, indicating it is the collector.

In the above process, the base, collector and Emitter of a transistor are checked with a multimeter. I have included the video below, which demonstrates how to find the base, collector, and Emitter of a transistor using a multimeter.