The 2N3904 is a versatile NPN bipolar junction transistor that can be used in a variety of low-power to medium-power applications. Its key features include NPN characteristics, low cost, high current gain, low power consumption, high speed, and relative ruggedness. This transistor is widely used in signal amplification, switching applications, noise circuits, oscillators, temperature sensors, current mirrors, and logic circuits.
2N3904 Features
1. General Purpose Transistor: The 2N3904 is suited to a broad range of applications, making it a reliable choice for various circuits, including amplification and switching circuits.
2. NPN Type: Being an NPN type transistor, it is primarily used for electron flow from the collector to the emitter, with its operation contingent on the current from the base to the emitter.
3. Low Cost: The 2N3904 is a very inexpensive component, making it an appealing choice for many circuit designs.
4. High Current Gain (hFE): Its typical hFE (DC current gain) is 40 at a collector current of 10 mA.
5. Low Power: This transistor is characterized by a low-power, with a maximum rating typically around 625 mW.
6. High Speed: It can operate at moderately high speeds, making it useful in frequency-based circuits.
7. Relative Robustness: The 2N3904 features a maximum collector current of 200 mA and can handle collector-emitter voltages up to 40 V, making it relatively sturdy for a small-signal transistor.
8. Compatible with Breadboard: Its physical package is typically TO-92, which is an easily handled size and compatible with breadboards and other prototyping and production systems.
9. Temperature Range: It is usually specified for operation over a temperature range of -55 C to 150 C, making it suitable for use in a wide variety of ambient environments.
2n3904 Transistor Pin configuration
2N3904 Pin Layout Diagram
The 2N3904 transistor has three terminals:
Emitter: The terminal that emits carriers, which are then diffused toward the base.
Base: This is the terminal that controls the transistor's operation by managing the number of carriers that reach the collector.
Collector: The terminal through which the transistor's carriers are collected.
2n3904 Spec Sheet
2N3904 MAXIMUM RATINGSRating
| Symbol | Value | Unit |
|---|
| Collector−Emitter Voltage | VCEO | 40 | Vdc |
| Collector−Base Voltage | VCBO | 60 | Vdc |
| Emitter−Base Voltage | VEBO | 6.0 | Vdc |
| Collector Current − Continuous | IC | 200 | mAdc |
Total Device Dissipation
@ TA = 25°C Derate above 25°C | PD | 625 5.0 | mW mW/°C |
Total Device Dissipation @ TC = 25°C Derate above 25°C | PD | 1.5 12 | W mW/°C |
| Operating and Storage Junction
Temperature Range | TJ, Tstg | −55 to +150 | °C |
2N3904 THERMAL CHARACTERISTICS| Characteristic | Symbol | Max | Unit |
|---|
| Thermal Resistance, Junction−to−Ambient | RJA | 200 | °C/W |
| Thermal Resistance, Junction−to−Case | RJA | 83.3 | °C/W |
2N3904 NPN BJT Circuit
The 2N3904 is an NPN Bipolar Junction Transistor which is often used in many different types of circuit designs including amplification and switching. A very basic example of a circuit using a 2N3904 NPN transistor is a simple transistor switch.
Here's a basic 2N3904 NPN transistor switching circuit:
2N3904 Equivalents
The 2N3904 is a commonly used NPN transistor due to its robustness and versatility. However, there are situations where you might want or need to use an equivalent transistor. 2N3904 equivalents include the 2N2222, 2N4401, BC547, BC548, PN2222, S8050, BC636 and BC639 transistors. Here are a couple of alternatives to the 2N3904:
2N2222: This NPN transistor is very common and has similar performance characteristics to the 2N3904. It can handle slightly higher current and power dissipation.
2N4401: It has similar performance to the 2N3904 but can manage a slightly higher maximum collector current.
BC547: A widely-used NPN transistor, especially in Europe. It has similar specifications.
BC548: Relatively equivalent to the 2N3904 in many applications and popular in European countries.
PN2222: Also an NPN transistor that stands as an equivalent to the 2N3904 in most applications.
S8050: A similar type of NPN transistor that can be used for general-purpose amplification and switching.
BC636 and BC639: These are power transistors with higher current and voltage ratings than the 2N3904.
Remember, while these transistors are often equivalent and interchangeable within a variety of circuits, they are not 100% identical. There might be slight differences in specs, such as max collector current and power dissipation.
2N3904 Applications
The 2N3904, like any transistor, must be used within its maximum current, voltage, power, and temperature ratings. The 2N3904 is a widely used, general-purpose NPN transistor that is suitable for a variety of low- to moderate-power applications. Some of the common applications include:
Signal Amplification: The 2N3904 is often used in the pre-amplification stage of audio and signal processing, where small signal levels need to be amplified.
Switching Applications: With suitable base current, the 2N3904 can be used to switch on or off other devices in a circuit, such as LEDs, relays, and other transistors.
Noise Circuits: Due to its low noise figures, the 2N3904 finds applications in noise generating circuits and white noise generators.
Oscillators: The 2N3904 can be used in oscillator circuits, such as those used in signal generators or electronic musical instruments.
Temperature Sensors: The base-emitter junction voltage decreases by about 2 mV/°C, making it a useful component in temperature measurement circuits.
Current Mirrors and Current Sources: The 2N3904, like other BJTs, can be used in current mirror and current source circuits, which are fundamental to many analog integrated circuits.
Logic Circuits: Transistors like the 2N3904 are fundamental to digital logic circuits where they act as electronic switches.
2N3904 Datasheet
Nantian ELectronics provides datasheets and manufacturer's guides for the 2N3904 from different manufacturers for download: