An electrical circuit consists of various electronic devices. Well, among all those various devices, the transistor plays an essential role in making a circuit successful. A transistor is mainly designed to convert the weaker signals of a circuit with a low resistance to a circuit with high resistance. Whereby transistors contain pinouts as a type of component. This article gives you a detailed insight into how pinouts affect the functionality of a transistor.

What are Transistors Pinouts?

A transistor comprises three basic components. These components consist of a Base, Emitter, and Collector. Generally, these transistor components act as pinouts of the transistor. However, Emitter considers the foremost pinouts which enable the transistor’s output.

After Emitter, then comes base. The base acts as a central core component of a transistor. The base not only controls the values but is also responsible for receiving the power supply connection. 

The collector comes in as the last yet largest component in a transistor. Because of its biggest size, it takes a greater carrier number in a transistor.

Identifying the Transistor Pinouts in Electronics 

Designing a PCB brings various challenges for manufacturers. However, identifying the connections of pins in various electronic devices is one of those hard challenges. These electronic devices include SCR, TRIAC, transistors, and other applications. Whereas to overcome these challenges, many professionals use datasheets. It helps them to identify the right connection for the pin and the place in a circuit. 

Let’s get into the guide which helps professionals identify the pins of transistors.

·       Bipolar Junction Transistor (BJT)

Transistors come in two forms, PNP and NPN. Both of these transistor forms are available in both metal or plastic casings. A transistor that has a plastic case comes in a flat frontal side with a serial arrangement of pins. However, if you want to identify the pins, face the flat side towards you and then count the number of pins. 

Both transistor forms have different arrangements of components. In the NPN transistor, the collector serves as the first pin, the Base as the second, and the Emitter as the third pin. This makes the CBE configuration. Whereas in the PNP transistor, we face different situations. Emitter acts as the first pin while Base acts as the second, and Collector as the third. Thus making the EBC configuration.

In metal casing transistors, the arrangement of pins comes circular instead of serial. However, find the tab present on the transistor rim. It helps in identifying the pins. NPN transistors with metal casing have Emitter as the nearest pin to a tab. The Collector is located on the opposite side of the Emitter. At the same time, the Base acts as a central core pin. However, you find a reverse situation in a PNP transistor with metal casings. The collector is the nearest pin to a tab; the emitter comes in the opposite direction, while the Base comes in the central part. 

Moreover, you must remember that this configuration may change with some exceptions. But mostly, you will most likely find these configurations. 

·       Field Effect Transistor (FET)

FET is a type of transistor with curved sides. Make sure to take the transistor facing you with curved sides. This helps in identifying the pins. Make sure to count the pins of FET in the reverse direction. In FET, Source acts as the first pin, then Gate, and Drain acts as the third and last.

·       (MOSFET) Metal Oxide Semiconductor Field Effect Transistor

MOSFET also uses the same configuration as FET. The configuration consists of Gate, then Drain, and then Source. However, in MOSFET, for identifying the pins, make sure to face the frontal side towards you. Then count the pins of the transistor starting from left to right side. The configuration of pins includes Source, then comes Drain, and the last Gate. This configuration is not considered synchronized. Therefore, make sure to use the datasheet, as it will help to identify the pins correctly.

·       (IGBT) Transistors Pinouts-Insulated Gate Bipolar Transistor

These kinds of transistors need practical IGBT such as GN2470 to locate the pins. For identifying the pins, make sure to hold the transistors raised side towards you. This helps you analyze the configuration of pins. First comes the cathode in a shorter form. Then Emitter is located on the right side of the cathode, while on its left side, there is Gate. 

Phototransistor and Transistor Pinouts

In phototransistors such as L14G2, make sure to hold it in a way that the curved surface faces you. Then count the pins. A collector comes first, then Emitter, and a Base comes in last.

Connecting Transistor with Circuit and Transistor Pinouts

The connection of a transistor with a circuit is generally the same despite its type. The connection needs components like an open switch, LED, a Resistor of 330-ohm, a Dual DC supply of power or batteries of 5AA, and a Transistor 2N3906.

Connect the emitter first with a connection of +3 Volt. Then connect the transistor’s base with an open switch. Then connect it with LED. The switch manages the transistors. Eventually, the transistor manages the LED.

Identifying Transistor Legs/Pins in 2023

Now you know about three pins of transistors, Emitter (E), Collector (C), and Base (B). You also go through different types of transistors. Now let’s dive into the methods which help in finding ways to identify the pins of transistors. There are basically three different yet easy methods. Pins are also known as legs or terminals of transistors. 

Well, the first method requires only the transistor’s datasheet. It does not need any device to go with it. At the same time, the second approach requires a multimeter. And the third approach needs a special and advanced type of device, a component tester.

·       Identify Transistor Legs

Identifying the pins of transistors plays an important role in the manufacturing process of circuits. Any wrong installation of the transistor could lead to the malfunctioning of the circuit. Or you may also damage or break the transistor. Transistors cost much; therefore, no one wants to afford their damage.

The following approaches help you understand easy ways to identify the pins of transistors without damaging them.

·       Data Sheet Method

The datasheet approach is the easiest yet cost-friendly way to identify the pins of transistors. This approach does not need any device does not require any advanced methods, just an available datasheet. Therefore, this approach serves as an ideal method if you want to save some extra money. 

However, to commence this approach, follow these steps.

1. Get the transistor.
2. Locate its number written on the body, or you can simply google it.
3. Then download its datasheet.
4. Simply go to the physical framework part of the datasheet.
5. Then follow the exact steps from the datasheet and place the transistor.
6. Compare the pins. Put the transistor over the screen facing the same side. 
7. And here you get your result
8. Ensure to mark the pins with their names or just symbols E, B, and C.

The only way to achieve the desired result is to put the transistor in the same as it is shown in a datasheet. For instance, if the transistor on the data sheet is facing you, then place the transistor in an exact way facing you.

Finding the datasheet can sometimes cause difficulty. But you can find it for sure. Instead of Google, in rare cases, you may use other search engines too. You can find the sheet there easily. This approach seems easy, yet it is time-consuming at the same time.

·       Using A Multimeter

This approach needs a digital multimeter. Moreover, it also needs some advanced technical knowledge of transistors. To commence this approach, follow these steps.

1. Turn the multimeter on. Then configure the meter to the diode testing mode.
2. Connect the red (positive) side to a V port. Whereas connecting the black ( negative) with a COM port.
3. The central pin of a transistor acts as a Base (B) pin.
4. Place the positive or red pin over the base terminal.
5. Then connect the negative with the right terminal. Make sure to note multimeter values.
6. Then connect the negative with the left terminal. Again note the values.
7. This shows that the highest value acts as an emitter, whereas the lowest value acts as a collector pin.

Make sure to use paper to note down the values, as the values may have close estimates so they won’t mix.

·       Using M328 Component Tester

The last approach is advanced and quite intriguing. This approach requires a special and advanced type of device called an electrical component tester. There are various types of component tester devices available in the market. But we are going to use an M328 electrical component tester today. Its user-friendly, reliable, and less expensive features make it ideal to use more following steps show how to identify the pins of transistors using this device.

1. First, turn the M328 tester on.
2. Place the transistor in a device socket.
3. You can put the transistor in any direction. It won’t affect the result.
4. Press the button on the test.
5. You can see the correct configuration of pins over the device screen. 
6. The screen shows each terminal with their names on it. Collector, emitter, and base.

This method proves suitable for any form of transistor. Moreover, this M328 electrical component tester can also help in identifying various other types of components along with their pins. For instance, diodes, LEDs, and SCR.

This tester not only helps in identifying the pin configuration but also helps in identifying the transistor type. For instance, it can easily identify BJT and MOSFETs or even tell the PNP or NPN form. Moreover, it also provides DC beta and values of forward voltage, which seems helpful in analyzing and designing the circuit. Additionally, you can also analyze whether the transistor is good or bad.

Facts to Think When Specifying The Pins Of Transistors

·       Transistor Types

Transistors come in various forms and types. Some famous transistors include Field-Effect or FET and Bipolar Junction or BJT. The configuration of the pin may also vary in each type. Therefore, ensure to identify the transistor first and then identify the pins.

·       Packaging 

Transistors are available in several types of packaging. Some come in surface mount, while some come in through-hole packaging. The configuration of pins may vary in each type of packaging. Therefore, make sure to identify the type of package before recognizing the pins of the transistor.

·       Pin-Layout

The layout of a pin generally includes three types of pins. Collector, Emitter, and the Base. In BJTs type of transistors, the base comes in the middle of the transistor while the other two emitters and collector are present on the opposites of each other. However, in FETs types of transistors, they contain Drain, Gate, and source pins which act corresponding to the Emitter, Base, and Collector of BJTs accordingly.

·       Pin Markings

You can also mark the pins of transistors with symbols, letters, or numbers to mention their operating function. However, understanding these symbols and markings helps in identifying each pin function. 

·       Pin Functions

Each transistor pin operates especially with a specific goal. The collector acts as the receiver, which collects the current. The emitter emits the current. At the same time, the base manages the flow of current between the emitter and collector pin. 

Pin Identification Of Diodes

·       Light Emitting Diode (LED)

You can easily identify the pins of LEDs by just looking over them. It contains a straight pin which acts as a positive pin. The flattened side acts as a negative pin. However, this may differ in advanced LEDs. The longer lead acts as a positive pin, whereas the shorter lead acts as a negative pin. 

·       Laser Diode

In diodes such as DL-3149-057, make sure to hold the diode while the curved side is facing toward you. This way, the cathode serves as the first pin, then comes the general pin, and the anode comes in the last.

·       PN Junction Diode

In PN junction-type diodes, the nearest lead to the ring is the cathode, while the other one is the anode.

·       Photodiode

However, while identifying the configuration in photodiodes such as QSD2030F, make sure to hold it is facing the curved part. Thus, this cathode acts as a shorter terminal, and the anode acts as a longer terminal.

Pin Identification Of Different Integrated Circuits

·       TSOP Sensor

The curved sides of TSOP-type sensors contain pins from the left side. The ground pin comes first, then Vcc, and the Output pin the last.

·       Motor Driver IC L293D

The Motor Driver Integrated Circuit also contains one curved edge. It contains 1 to 8 pins on the left side of a curve. At the same time, the right side of the curve contains from 9 to 16 pins from the bottom side right to the top side. 

·       Relay Driver IC

The pin configuration of the Relay Driver Integrated Circuit is the same as that of the Motor Driver Integrated Circuit. It has a slight difference in curved sides. The one edge of this IC is completely taken out from the middle of it, which aids in making a curved surface. 

Conclusion

The transistor acts as an active and essential electrical component in an electric circuit which assists in application and switching purposes. Transistors need technical and complex knowledge to work on, such as how to recognize the transistor’s pins. 

This is one of the basic yet essential things you really need to understand. Without the technical knowledge of pin or leg configuration, one may produce damaged circuits. 

However, you may not want a damaged circuit or transistor. Therefore, just follow three simple methods of configuration which help in configuring the pins properly. The first method focuses on the usage of the datasheet of a transistor and then matches the values with physical values. Thus, this enables you to find the correct configuration of the pin in a transistor. Moreover, the 2nd approach focuses on a digital multimeter. 

First, the transistor goes through a diode test using a multimeter. It then helps in finding the appropriate configuration of pins.

The third and last approach focuses on the electrical component tester. This component tester device helps in identifying, verifying, and analyzing several electrical components. However, just place a transistor in the device and on it. This gives correct and appropriate pin configuration within seconds.