There are different types of NPN transistors and each is used for its special application areas. Among these transistors is the 2N3904 NPN transistor. What is it, where is it used and how does it work?
We have all the answers to such questions. Read on as we dissect all you should know about the 2N3904 NPN transistor.
What is an NPN transistor?
First things first, let’s understand the basics of an NPN transistor. NPN means that the PN junction is biased so that the N-type material is more conductive than the P-type material.
The transistor has three terminals, namely, collector, base, and emitter.
The collector terminal of an NPN transistor is where the current enters and flows out from the other end of the collector terminal.
The emitter terminal is where the current enters the base terminal and flows out through it to the other end of the emitter terminal.
The base terminal controls whether current can flow from emitter to collector or not.
When a small voltage is applied to it, there will be no flow of current from emitter to collector; when a large voltage is applied, there will be a large flow of current between emitter and collector.
This property makes this kind of transistor an active device because it amplifies small signals into bigger ones.
The 2N3904 NPN transistor
Now that you know what an NPN transistor is all about, let’s proceed to what matters.
The first thing to note is that this transistor is a general purpose NPN transistor.
It can be used for amplifying signals, acting as a switch, and even rectifying AC signals.
The 2N3904 transistor is made of silicon and copper.
The silicon material provides the P-type semiconductor while the copper provides the N-type semiconductor.
This configuration makes it possible for current to flow through this device from emitter to collector when there is a small voltage applied to its base terminal. Just like other NPN transistors, this one also has an emitter, base, and collector terminal.
Design and structure of 2N3904 NPN transistor
As we have already mentioned, the 2N3904 NPN transistor comprises three terminals-base, emitter, and collector. But, how are these terminals arranged and organized in a transistor system?
This transistor is characterized by a pinout structure. This means that the terminals are designed to form pin-like structures where each pin represents a respective terminal.
The base terminal is represented by pin 1 and the other two terminals are represented by pin 2 and 3 respectively.
It is important to note that in most cases, the emitter is labeled as “E”, while the collector is labeled as “C”.
The arrow symbol on each pin represents the direction of the current flow. For example, if there is a small voltage applied to the base terminal and if there is no voltage applied to the emitter or collector then, the current will flow from emitter to collector and this current will be proportional to the voltage applied at the base terminal.
Also, it should be noted that in most cases, this transistor has an arrow on its top surface pointing towards its emitter. This arrow indicates that following this arrow in a clockwise direction from its base terminal leads us towards its emitter.
2N3904 NPN transistor ratings
It is imperative to know that 2N3904 NPN transistors have power ratings. Their performance and relevance are determined by these ratings.
Usually, the ratings of a transistor that you buy will depend on its circuit requirements. If your circuit has a high power demand, then you will go for the transistor with high power ratings.
If you use a low-rated transistor on a demanding circuit, chances are it will blow out.
Here is a sample of the 2N3904 NPN transistor ratings:
-C-E voltage. This refers to the voltage between the collector and emitter. nIn most transistors, it is 40V
-C-B voltage: this refers to the voltage between the collector and the base. It is usually 60V in an NPN transistor.
-E-B voltage: this refers to the voltage between the emitter and base. It is usually 50V in an NPN transistor.
-Collector current: this refers to the current that flows from the collector to the base. It is usually 200mA in an NPN transistor.
-Emitter current: this refers to the current that flows from the emitter to the base. It is usually 50mA in an NPN transistor.
2N3904 NPN transistor applications
Now let’s look at the real-world applications of this transistor:
-Used as a control switch: 2N3904 NPN transistor is used as a switch where it controls heavy loads. How is this possible? One unique feature about this transistor is low saturation voltage and this is the main reason it can easily operate as a power switch without any impediments.
-Used as a control amplifier: 2N3904 NPN transistor is used as an amplifier in the form of an emitter follower. This is a simple circuit and it can be easily constructed by connecting the input to the base of the 2N3904 NPN transistor and its collector to the output.
-Used as a switching regulator: this type of transistor can be used as a switching regulator. It is usually used in two-stage voltage boosters or buffer circuits where they are connected in series. The output voltage will be determined by how many stages are connected between its base and collector terminal. The output voltage will also depend on how much current flows into each stage from its base terminal.
-Used as a current limiter: this type of transistor is also used to limit current flow into its base terminal where it breaks down under high currents leading to breakdown voltages that are very dangerous for electrical equipment components like transistors and LEDs, etc.
-Used as a general purpose transistor: this type of transistor can be used in many different applications that require a transistor to perform its functions. This is the most common and widely used type of transistor because it has excellent performance for low voltage, high current, and high power applications.
-Used to switch the DC supplies: this type of transistor can be used to switch the DC power supplies where it is connected from its collector to base terminals and then return the DC supply by connecting its collector to the ground using a resistor. The resistor value will determine how much voltage will be output by this circuit.
-Used in relay circuits: this type of transistor is used in switching applications where it is connected inside an electronic relay circuit where it can be switched on/off by sending a signal from one side of the relay circuit.
Features and benefits of 2N3904 NPN transistor
Since one of our goals is to help you make a smart purchasing decision, we are going to highlight key features and the top benefits of 2N3904 NPN transistors:
-Low saturation voltage: when the collector-emitter voltage is low, this type of transistor will have a low collector-emitter voltage. This means that it will have less power dissipation and when it is connected to a circuit, the current will be lower.
-Excellent voltage gain: This type of transistor has good gain. When you connect its collector to base terminals, the base current will be high but when you connect its collector to ground terminals, the base current will be very low.
-Small size: Since this type of transistor has a small size, it can fit in tight spaces where other transistors cannot fit. This is one of its major benefits because it makes it easy for this type of transistor to be used in many different applications such as light bulb applications and switching circuits.
-Low input voltage: this type of transistor will have less input voltage because it has a small emitter-base voltage which means that the collector-emitter voltage will be quite low.
-Good power dissipation: When you connect this type of transistor to a circuit, its collector current will be very high as compared to its base current. This is one of its major benefits because when it is connected to an application, the heat generated from the transistor’s power dissipation will not affect other parts in the circuit.
-Low base resistance: this type of transistor has low base resistance which means that it can easily be used in many different types of applications such as light bulbs and switching applications.
-Low noise: This is another benefit of using 2N3904 NPN transistors because they do not generate much noise.
Where to buy the 2N3904 NPN transistor?
You can easily find a 2N3904 NPN transistor from the manufacturer. If you want to buy them from a local supplier, you can contact them and they will give you the best price.
You have to provide your own package and they will send it to you after they receive payment.
And in case you want to buy 2N3904 NPN transistors in China, you can get a sourcing agent to help you. They will direct you to the right manufacturers and suppliers of the transistors.
ICRFQ is one of the reliable sourcing agents for the 2N3904 NPN transistors. We will ensure that you get the right transistors in China at a reasonable price.
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