You can find the 2N5551 transistor in circuits that need high voltage but low current. This device is an NPN bipolar junction transistor. It is made for switching and amplifying signals. You can use it in audio amplifiers, digital switches, and voltage regulators. The 2n5551 npn amplifier transistor is special because it can handle up to 160V across collector-emitter. It also supports 600mA current and has fast switching speed. As an npn transistor, it gives stable gain and saves energy. Its strong npn design lets you power LEDs, control integrated circuits, and manage display drivers. The 2n5551 datasheet shows its low saturation voltage and good thermal management. This makes it a great choice for many uses where switching and amplifying are important.
Key Takeaways
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The 2N5551 is an NPN transistor. It is made for high voltage up to 160V. It can handle low current up to 600mA. People use it for switching and amplifying signals.
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The pinout is easy to remember. Hold the flat side toward you. Pin 1 is the emitter. Pin 2 is the base. Pin 3 is the collector. You must connect the pins the right way for it to work.
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This transistor switches fast and gives strong signal gain. It comes in a small TO-92 package. This package fits well on breadboards and PCBs.
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You can use other transistors like 2N5550 or BC639 instead. But you should always check their datasheets first. Make sure they work for your circuit.
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The 2N5551 works in audio amplifiers, digital switches, and display drivers. You need to set the bias and control heat. This keeps the transistor safe and working well.
2N5551 Pinout
Pinout Diagram
When you work with the 2N5551 transistor, you need to know the correct 2n5551 pinout. The 2N5551 comes in a TO-92 package, which is a small, plastic case with three leads. If you look at the flat side of the transistor facing you, you will see three pins lined up from left to right. The 2n5551 pin configuration follows a standard order for this package.
Here is a simple table that shows the 2n5551 pinout:
| Pin Number | Terminal |
|---|---|
| 1 | Emitter |
| 2 | Base |
| 3 | Collector |
Tip: Always check the flat side of the transistor to match the pin numbers correctly.
Pin Functions
Each pin on the 2N5551 has a special job. You need to connect each one to the right part of your circuit for the transistor to work well.
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Emitter (Pin 1): This pin lets current flow out of the transistor. You usually connect it to ground or the negative side of your power supply.
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Base (Pin 2): This pin controls the transistor. When you apply a small current here, it allows a larger current to flow from collector to emitter.
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Collector (Pin 3): This pin receives the main current. You connect it to the load or the positive side of your circuit.
The 2n5551 pin configuration is easy to remember if you always look at the flat side. The emitter is on the left, the base is in the middle, and the collector is on the right.
Identifying Pins
You can identify the pins of the 2N5551 by holding the transistor with the flat side facing you. Start counting from the left. Pin 1 is the emitter, pin 2 is the base, and pin 3 is the collector. This pin configuration matches many other NPN transistors in the TO-92 package, but you should always double-check before soldering.
If you want your circuit to work safely, follow these tips for handling and mounting:
| Aspect | Recommendation |
|---|---|
| Voltage Handling | Keep supply voltage at least 5-10V below max rating (160V) to avoid damage and extend lifespan. |
| Current Management | Use appropriate base resistor to keep collector current below 600mA, preventing thermal runaway. |
| Thermal Management | Maintain operating temperature between -55°C and +150°C; use heat sinks or cooling methods. |
| Biasing | Employ voltage divider networks for stable base biasing to avoid saturation or cutoff states. |
You can see that the 2n5551 pinout is simple, but you must connect each pin correctly. If you mix up the pins, the transistor will not work, and you might damage your circuit. Always check the 2n5551 pin configuration before you start building.
Features
2N5551 Transistor Features
The 2n5551 transistor has many helpful features for electronics. This npn transistor works in circuits that need high voltage and low current. You can use it to make signals bigger or to turn things on and off. The 2n5551 comes in a TO-92 package, so it is easy to use on a breadboard or PCB. It does not have lead or halogen, so it is safer for you and better for the earth. The 2n5551 npn amplifier transistor gives strong signal gain with little input current.
Here are some important features you should know:
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NPN bipolar type
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High collector-emitter voltage (up to 160V)
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Collector current up to 600mA
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High dc current gain (hFE) around 80
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TO-92 plastic package
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Lead-free and halogen-free construction
Note: The 2n5551 transistor is a smart pick if you want good performance for switching or amplifying.
Electrical Specs
You should always look at the main specs before using the 2n5551 transistor. These specs help you see if this npn transistor is right for your project. The table below shows the most important electrical details:
| Parameter | Value |
|---|---|
| Collector-Emitter Voltage (Vce) | 160V |
| Collector-Base Voltage (Vcb) | 180V |
| Emitter-Base Voltage (Veb) | 6V |
| Collector Current (Ic) | 600mA |
| DC Current Gain (hFE) | 80 (typ.) |
| Power Dissipation (Ptot) | 625mW |
| Transition Frequency (ft) | 100MHz |
These specs show the 2n5551 transistor can handle high voltage and medium current. You can use it in lots of different circuits.
Maximum Ratings
You must follow the maximum ratings to keep your 2n5551 transistor safe. If you go over these limits, you could break the transistor. Here are the main maximum ratings:
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Maximum collector-emitter voltage: 160V
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Maximum collector current: 600mA
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Maximum power dissipation: 625mW
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Operating temperature range: -55°C to +150°C
The 2n5551 transistor is special because it handles high voltage but is still small. You can use this npn transistor for making signals bigger or for fast switching. Its features make it a top choice for audio, RF, and general projects.
2N5551 Datasheet Equivalents
Equivalent Transistors
Sometimes you need to replace the 2N5551 in your project. There are other 2n5551 equivalent transistors you can use instead. Some examples are 2N5550, NTE194, 2N5833, BC637, BC639, BC487, and 2N5551K. These parts have similar features, but you should check their main specs first. For example, the 2N5550 is a lot like the 2N5551, but it cannot handle as much voltage. BC639 and NTE194 are also good choices for many circuits. If you want to use a 2n5551 equivalent, try it in your project to see if it works.
Tip: Always look at the datasheets for any equivalent before you swap transistors in your design.
Comparison Table
The table below shows the main differences between the 2N5551 and some of its equivalents. This helps you choose the best part for your project.
| Parameter | 2N5551 | 2N5550 | BC639 / NTE194 (Equivalents) |
|---|---|---|---|
| Maximum Collector-Emitter Voltage (Vce) | 160 V | 140 V | Not specified |
| Maximum Collector Current (Ic) | 600 mA | 600 mA | Not specified |
| DC Gain (hFE) Range | 40 - 300 | 80 - 250 | Not specified |
| Transition Frequency (fT) | ~100 MHz | 100 - 300 MHz | Not specified |
| Power Dissipation (Pd) | 625 mW | Not specified | Not specified |
The 2N5551 is special because it can handle more voltage and switches fast. The 2N5550 is almost the same but works with less voltage. BC639 and NTE194 are also used as replacements, but their datasheets do not always show every detail. You should always test a 2n5551 equivalent in your real circuit.
Complementary PNP
If you need a matching PNP transistor for the 2N5551, you can use the 2N5401. This PNP part is made to work well with the 2N5551. It is good for push-pull amplifier circuits or other designs that need both NPN and PNP types. The 2N5401 can handle about the same voltages and currents, so it is a good match for the 2N5551.
Note: Using a complementary PNP like the 2N5401 helps you make balanced amplifier stages or switching circuits.
Applications
Amplification
The 2n5551 npn amplifier transistor is used to make signals stronger. It works well in audio amplifiers, especially where you need to boost voltage. You can use it to make weak sounds louder without much distortion. In these circuits, you use a voltage divider for the base. An emitter resistor helps keep things steady. A collector load resistor controls the output. This setup gives you clear and steady sound for music or voice. The 2n5551 can handle high voltage and switches quickly. That makes it good for both audio and some RF signal boosting. You might also see it in driver stages, like Darlington pairs, to help with bigger loads.
Switching
The 2n5551 is also great for turning things on and off. You can use it in digital circuits, display drivers, and power systems. In these circuits, the 2n5551 acts like a fast switch. It can handle high voltages, so it works for relays, LEDs, or other loads. Engineers use it in special tests to make very quick pulses for testing SiC diodes. This shows it can handle fast voltage changes in tough jobs. When you use the 2n5551 for switching, always be careful. Make sure it stays cool, is set up right, and starts safely to avoid damage.
Tip: For safe switching, match your transistors and watch idle current to stop heat problems.
Typical Circuits
You can make many helpful circuits with the 2n5551. Here is a simple diagram for using the 2n5551 npn transistor to make signals stronger:
+Vcc
|
R1 (Collector Load)
|
Collector
|
2N5551
|
Emitter -- R2 -- GND
|
Base
|
R3, R4 (Voltage Divider)
|
Input Signal
This basic amplifier uses resistors to set up the transistor and keep it steady. You can use it for audio preamps or to make small signals bigger. For switching, put the load (like an LED or relay) on the collector. Use a base resistor to turn it on or off. In power or display circuits, the 2n5551 switches loads fast and works well.
Note: Always look at the datasheet before you pick where to use the 2n5551.
Now you know how to use the 2n5551 for both switching and making signals stronger. The 2n5551 transistor lets you do many things, from boosting signals to fast switching. Try it in your next project to see how well it works.
Package & Datasheet
TO-92 Dimensions
When you build a circuit, you need to know the transistor’s size. The 2N5551 uses a TO-92 package. This package is small and fits well on breadboards or PCBs. Its compact shape lets you use it in tight spots.
Here are the usual TO-92 dimensions for PCB design:
| Parameter | Value (mm) |
|---|---|
| Body Width | 4.5 |
| Body Height | 4.0 |
| Body Thickness | 3.5 |
| Lead Pitch | 1.27 |
| Lead Length | 14.0 |
| Overall Height | 17.0 |
Tip: Always check the 2n5551 datasheet for exact sizes before making your PCB. Even small size changes can affect how the transistor fits.
The TO-92 package has three leads spaced the same distance apart. This makes it simple to put the 2N5551 into most PCB layouts.
Datasheet Specs
You should always read the 2n5551 datasheet before using this transistor. The datasheet gives you important details, like electrical ratings and pin layout. You will see the highest voltage, current, and power ratings in the datasheet. It also shows safe ways to use the transistor and gives example circuits.
Some main specs you will find in the 2n5551 datasheet are:
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Maximum collector-emitter voltage: 160V
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Maximum collector current: 600mA
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Power dissipation: 625mW
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DC current gain: 80 (typical)
You can also find sample circuits in the datasheet. These help you use the 2N5551 for switching or making signals bigger. If you want your circuit to work well, always use the official 2n5551 datasheet as your main guide.
Note: The datasheet is the best place for up-to-date info and safe design tips.
You have learned the key things about the 2N5551 transistor. Look at this table for a quick summary:
| Aspect | Details |
|---|---|
| Pinout | Emitter (1), Base (2), Collector (3) |
| Features | High voltage, fast switching, wide temperature range, TO-92 package |
| Specs | 160V max voltage, 600mA current, 625mW power, hFE up to 250 |
| Equivalents | 2N5550, BC639, NTE194, 2N5401 (PNP) |
| Applications | Audio/RF amplification, sensor interfacing, relay and LED driving |
You should always look at the official datasheet before building your circuit. Try the 2N5551 in your next project to see all the things it can do.
FAQ
What is the main use of the 2N5551 transistor?
You use the 2N5551 transistor for switching and amplifying signals. It works well in audio circuits, display drivers, and voltage regulators. You can also use it in projects that need high voltage and low current.
How do you identify the pins on a 2N5551?
Hold the flat side of the transistor facing you. The pins from left to right are emitter (1), base (2), and collector (3).
Always double-check the pinout before connecting to your circuit.
Can you replace the 2N5551 with another transistor?
Yes, you can use equivalents like 2N5550, BC639, or NTE194.
Check the datasheet for each part to make sure it matches your needs.
What is the maximum voltage the 2N5551 can handle?
The 2N5551 can handle up to 160V between collector and emitter.
Do not exceed this value to keep your transistor safe.
Is the 2N5551 suitable for audio amplifier projects?
Yes, you can use the 2N5551 in audio amplifier circuits. It gives good voltage gain and works well for preamp and driver stages.
Use proper biasing for the best sound quality.
Written by Jack Elliott from AIChipLink.
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