2N5551 can be described as an NPN amplifier transistor. Its amplification factor (hfe) is 80 when the current of the collector is 10mA. It also has good shifting properties thus allowing it to amplify low-level signals. Today, easybom will introduce the details about it. This article will be divided into below parts: 2N5551 Datasheet2N5551 Pinout2N5551 Equivalent2N5551 Transistor Applications, and so on.

Features of 2N5551 Transistor

The High DC Current Gain (hFE) is usually 80 when IC = 10mA

Continuous Collector Current : 600mA

The voltage of the Collector-Emitter: 160 V

The voltage of Collector-Base: 180V

The voltage of Emitter Base: 6V

Transition Frequency: 100MHz

2N5551 Pinout

Below is the 2N5551 Pinout:



Package / Case – TO-226-3, TO-92-3


Operating Temperature –   -55°C~150°C TJ

2N5551 Transistor Applications

Low power amplifiers

Current amplifiers

Small signal boosters

Audio or other signal amplifiers

Darlington pair

2N5551 Circuit

Below is the 2N5551 circuit:

Where to use 2N5551 Transistor?

The 2N5551 transistor is typically utilized to amplify audio signals or other low-power signals. It can be extensively utilized for amplification. A basic bare minimum circuit to allow a transistor to serve as an amplifier can be seen above. If you’re seeking an NPN transistor to use in your amplifier circuit, this transistor may be the best option.

2N5551 Equivalent 

You could use NTE194, 2N5833, 2N5088, 2N3055, and 2N5401 (PNP) as 2N5551 equivalents. You could find them on easybom.

How to use 2N5551 Transistor?

In the above circuit of 2N5551, the input sine wave of 8mV is amplified up to 50mV, as illustrated in the diagram. In the above circuit, the resistors R3 & R4 create a potential divider that determines the base voltage of the emitter. The Resistor R1 acts as the load resistor while the resistor R2 acts as the resistor that emits. The change in the value of RL can affect the amplifying of the output sound.

A transistor is usually an amplifier of current, which means that the current flowing through the base is amplified by the flow of current across the collector. The collector’s current will be amplified by about 80 times greater than the current in the base. Ic = βIb.

We could find that another current is the current of the emitter. The Emitter current is close to the value of the Collector current, but the differences between them can be determined by the value of α. The formula for the normal value of collector current is IE = IC + IB.

The output is derived from the Collector-Emitter voltage. The output voltage is influenced by the input voltage, but not the drop in voltage across the load resistor. So the output voltage (Vout) could be expressed as follows: Vout = VCE = (Vcc – ICRC) 

How to Safely Long Run a 2N5551 Transistor in a Circuit?

If used correctly, electronic components can be very reliable and last a long time. It is crucial to avoid exceeding the maximum rating of any component. Instead, use it at least 20% below its maximum rating. This will ensure long-term performance. The 2N5551 should be used in this way. The maximum drain-source voltage is 30V. The drain-gate voltage must be below 24V, and the gate-source should not exceed -24. Limiting the drain current to 25mA is recommended. Do not load it with more than 20mA. Also, do not store or use the transistor below -55 degrees centigrade or above +150 degrees centigrade.

Everything You Need to Know About 2N5551 Transistor in Electronics

How does an NPN transistor work as an amplifier?

A transistor serves as an amplifier and amplifies the power of weak signals. Its DC bias voltage that is applied to the base junction of the emitter allows it to remain in a forward-biased state. This bias remains forward regardless of the signal’s polarity.

What does an NPN transistor do?

The NPN transistor consists of a P-type material placed between two N-type materials. It amplifies the weak signal that is entering the base. It creates strong amplify signals at the collector’s end.

What is the difference between an NPN and PNP transistor?

The primary difference between an NPN as well as a PNP transistor is that the NPN transistor is activated when current is flowing through the transistor’s base. In this kind of transistor, the current is flowing through the collector to the emitter. However, the PNP transistor is turned ON in the absence of any current flowing through its base.

2N5551 vs 2N2222

What is 2N5551?

2N5551 can be described as an NPN amplifier transistor. Its amplification factor (hfe) is 80, when the current of the collector is 10mA. It also has good shifting properties thus allowing it to amplify low-level signals.

What is the use of 2N2222 transistor?

The 2N2222 is designed for general-purpose low-power amplifying and switching functions. It is specifically designed for low-to-medium current, low power, and medium voltage. It could operate at moderately high speeds.

BC547 vs 2N2222

Can I use 2n2222 instead of BC547?

Yes. It doesn’t really matter if you use a 2n2222 or a BC547 NPN transistor. The circuit can be updated at any time, but you need to check Ic and Vceo within the information sheet.

What is the difference between BC547 and BC548?

These NPN transistors have many similarities and characteristics. However, they differ in their voltage ratings. The BC546 and BC547 are basically the same as the BC548, but with higher breakdown voltages. The BC549 is a low noise version, while the BC550 is a high-voltage and low-noise version.

BC547 vs BC548 

What is BC548 transistor?

The BC548 is an all-purpose NPN bipolar junction transistor widely utilized for electronic devices. It is often the first bipolar transistor that enthusiasts encounter. 

Can we use BC548 instead of BC547?

Absolutely not. BC547 is an NPN. However, BC548 is a PNP transistor. Both of them are not substitutes for each other.

Package Dimensions 

Below is the picture of the 2D Model and Dimensions from the 2N5551 Datasheet will be useful to know the package type and dimensions.

2N5551 Datasheet 

Download the 2N5551 datasheet below:

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