2N3904BU: NPN general-purpose amplifier and switch, 40V VCEO, 200mA IC, 100MHz

The 2N3904BU by onsemi is an NPN transistor designed for general-purpose applications, functioning both as an amplifier and a switch. It supports a collector-emitter voltage (VCEO) of up to 40V and can handle a continuous collector current (IC) of up to 200mA, making it suitable for a wide range of applications in electronic circuits. The transistor's utility as an amplifier extends to frequencies up to 100MHz, demonstrating its versatility in signal processing tasks.

Key characteristics include its ability to operate within a wide temperature range (-55 to +150°C), ensuring reliability under various environmental conditions. The device also features low saturation voltages and a range of DC current gain (hFE) values, facilitating efficient operation in both saturated and active regions. These attributes, combined with its thermal performance, make the 2N3904BU a reliable choice for designers focusing on efficiency and thermal management.

Key Specifications and Features

  • Collector-Emitter Voltage (VCEO): 40V
  • Collector-Base Voltage (VCBO): 60V
  • Emitter-Base Voltage (VEBO): 6.0V
  • Collector Current - Continuous (IC): 200mA
  • Operating and Storage Junction Temperature Range: -55 to +150°C
  • Total Device Dissipation (PD): 625mW
  • DC Current Gain (hFE): 40 to 300
  • Collector-Emitter Saturation Voltage (VCE(sat)): 0.2V to 0.3V
  • Base-Emitter Saturation Voltage (VBE(sat)): 0.65V to 0.95V
  • Current-Gain - Bandwidth Product (fT): 300MHz

2N3904BU Datasheet

2N3904BU datasheet (PDF)

2N3904BU Substitutes
Equivalent alternate parts that may serve as a substitute for 2N3904BU, most popular parts first


  • Signal amplification
  • Switching applications
  • Audio amplifiers
  • Oscillator circuits



General information

NPN transistors are a fundamental component in electronics, serving as building blocks in both digital and analog circuits. They operate by allowing a small current at their base terminal to control a larger current flowing between the collector and emitter terminals. This characteristic makes them suitable for a range of applications, including amplification and switching.

When selecting an NPN transistor, key parameters such as the collector-emitter voltage, collector current, and DC current gain are important considerations. These parameters determine the transistor's ability to handle the voltages and currents in a circuit, as well as its efficiency in amplifying signals. Additionally, the frequency response is crucial for applications requiring high-speed operation or signal processing at specific frequencies.

Thermal management is another critical aspect, as transistors can generate significant heat during operation. The device's power dissipation capability, along with its thermal resistance, informs the design of heat sinking and other thermal management strategies to ensure reliable operation over its intended temperature range.

Overall, the choice of an NPN transistor depends on a careful evaluation of its electrical characteristics, thermal performance, and suitability for the intended application. Understanding these aspects is essential for optimizing circuit performance and reliability.

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