2N3904: Overview,parameter,Main uses,Features,application fields,working principle and alternative models


2N3904 Transistor Detailed Introduction:


The 2N3904 is a common general-purpose NPN bipolar junction transistor (BJT) used for amplification and switching purposes in electronic circuits.



  • Collector Current (Ic): Maximum current that can flow through the collector.
  • Collector-Base Voltage (Vcbo): Maximum voltage between collector and base.
  • Collector-Emitter Voltage (Vceo): Maximum voltage between collector and emitter.
  • DC Current Gain (hFE): Gain of the transistor under specific conditions.
  • Power Dissipation (Pd): Maximum power the transistor can handle.
  • DataSheet

    2N3904 PDF

Main Uses:

  • Amplification: Boosting signal strength in audio and RF circuits.
  • Switching: Controlling higher current/voltage loads with a low-power signal.
  • Oscillator Circuits: Forming the core element in timing circuits.
  • Signal Conditioning: Modifying signals in sensors and signal processing circuits.


  • Low Cost: Widely available and inexpensive.
  • Small Package: Typically comes in a compact TO-92 package.
  • High Frequency Capability: Suitable for RF applications.
  • Moderate Power Handling: Can handle moderate power levels.
  • Easy to Use: Commonly used in educational settings due to its simplicity.

Application Fields:

  • Audio Amplification: Building audio preamplifiers and small audio systems.
  • Switching Circuits: Driving relays, LEDs, and small motors.
  • Signal Processing: Modifying signals for various sensor applications.
  • RF Circuits: Building oscillators and RF amplifiers in communication systems.

Working Principle:

  • Biasing: Applying proper voltage levels to the base terminal.
  • Amplification: Small current flowing from base to emitter controls a larger current flow from collector to emitter.
  • Saturation/Cut-off: Switching between on and off states based on base current.

Alternative Models:

  • 2N2222: Another common general-purpose NPN transistor.
  • BC547: Similar NPN transistor with slightly different specifications.
  • 2N4401: NPN transistor with higher current and power ratings.

The 2N3904 transistor is a versatile component used in a wide range of electronic circuits for amplification and switching. Variants like the 2N2222 and BC547 offer similar functionality with slight variations in parameters. Each alternative model may have specific advantages depending on the requirements of the circuit being designed. For detailed technical specifications and performance characteristics, refer to the datasheets provided by the manufacturers of these transistors.