2N3904BU onsemi 2N3904BU NPN Bipolar Junction Transistor, 40 V, 200 mA, TO-92-3, 625 mW, 300 MHz

onsemi 2N3904BU NPN general-purpose amplifier / switch transistor

The onsemi 2N3904BU is a reliable, industry-recognized NPN bipolar junction transistor designed for general-purpose amplification and switching across a broad range of electronic applications. With its 40 V collector-emitter voltage, 200 mA continuous collector current capability, and 300 MHz transition frequency, this device offers an effective balance between signal performance, switching speed, and design simplicity. It is housed in a TO-92-3 through-hole package, making it especially suitable for conventional PCB assembly, prototyping, industrial control boards, and legacy equipment maintenance.

For OEMs, contract manufacturers, and industrial buyers, the 2N3904BU remains a highly practical transistor choice because it supports both low-power signal amplification and fast switching tasks in one compact component. It is widely used in driver stages, signal conditioning circuits, small-signal amplification, interface designs, and discrete transistor-based control architectures. In B2B sourcing environments, components like the 2N3904BU are valued not only for their electrical performance, but also for their long-standing market familiarity, straightforward integration, and ease of replacement in existing designs.

Built for Versatile Amplifier and Switching Designs

One of the core advantages of the 2N3904BU is its versatility. onsemi positions this device as a general-purpose amplifier and switch, with a useful dynamic range extending to 100 mA as a switch and to 100 MHz as an amplifier. This makes the transistor highly adaptable in circuits where engineers need a dependable NPN device for signal gain, level shifting, or load control without introducing unnecessary complexity.

In amplifier applications, the transistor provides solid DC current gain characteristics across multiple operating points, making it suitable for low-power analog stages, preamplifier blocks, and signal processing sections in control electronics. In switching designs, its fast timing performance supports efficient digital-style on/off operation in applications such as relay driving, indicator control, low-current actuation, and logic interface circuits. Designers working in industrial electronics, consumer products, telecom accessories, and instrumentation can use the 2N3904BU as a practical building block for cost-effective circuit development.

Electrical Performance for Stable Circuit Operation

The 2N3904BU offers a robust set of electrical characteristics that support dependable performance in everyday circuit conditions. Its 40 V collector-emitter breakdown voltage provides sufficient margin for many low- to medium-voltage designs, while the 200 mA continuous collector current rating allows the transistor to handle a wide range of small-load control functions. The 625 mW power dissipation capability further contributes to stable operation in compact board-level implementations when proper thermal design is observed.

The device also delivers a typical current gain-bandwidth product of 300 MHz, making it attractive for engineers who need a transistor capable of responding well in higher-frequency signal paths. Low parasitic capacitance values, including 4.0 pF output capacitance and 8.0 pF input capacitance, help support cleaner signal behavior and predictable response in sensitive analog and switching circuits. These characteristics are especially beneficial in compact embedded systems where discrete components must maintain consistent performance without excessive compensation or redesign.

Specifications

• Manufacturer: onsemi
• Part Number: 2N3904BU
• Product Type: Single Bipolar Transistor (BJT)
• Transistor Polarity: NPN
• Collector-Emitter Voltage (VCEO): 40 V
• Collector-Base Voltage (VCBO): 60 V
• Emitter-Base Voltage (VEBO): 6.0 V
• Continuous Collector Current (IC): 200 mA
• Power Dissipation (PD): 625 mW
• Transition Frequency (fT): 300 MHz
• Package: TO-92-3 / TO-92 3L
• Mounting Type: Through Hole
• Operating / Storage Junction Temperature Range: -55°C to +150°C
• Typical Output Capacitance (Cobo): 4.0 pF
• Typical Input Capacitance (Cibo): 8.0 pF
• Typical Noise Figure: 5.0 dB

Through-Hole TO-92-3 Package for Easy Integration

The through-hole TO-92-3 package remains a preferred choice in many B2B manufacturing and service environments, particularly where durability, straightforward insertion, and field replacement matter. The 2N3904BU is well suited for wave soldering and traditional PCB assembly workflows, and it also fits development boards, educational kits, and repair applications where through-hole components continue to offer practical advantages.

For buyers serving industrial maintenance, aftermarket repair, and low- to medium-volume equipment production, through-hole transistors like the 2N3904BU simplify procurement and assembly planning. The familiar TO-92 footprint reduces design friction and makes cross-project standardization easier. It is also a useful choice for applications requiring manual assembly or where technicians need easy identification and replacement during servicing.

Suitable Applications Across Multiple Industries

Because of its balanced electrical characteristics and broad usability, the onsemi 2N3904BU can be deployed in a wide variety of applications, including:

Small-Signal Amplification

The transistor is suitable for audio pre-stage circuits, sensor front-end amplification, and general signal conditioning blocks where stable NPN gain is needed.

Switching and Driver Circuits

It can be used for low-current switching tasks, relay or LED driving, transistor logic interfaces, and control signals in embedded systems.

Industrial and Commercial Electronics

The 2N3904BU is a practical fit for control boards, instrumentation modules, automation interfaces, power management support circuits, and repair or replacement programs for legacy equipment.

Education, Prototyping, and Development

Its through-hole format and well-known behavior make it an excellent component for engineering validation, proof-of-concept builds, and laboratory use.

Why Choose the onsemi 2N3904BU

For professional buyers and hardware designers, selecting a transistor is not just about headline voltage and current ratings. It is about securing a component that is easy to design in, easy to source, and dependable across real production conditions. The onsemi 2N3904BU answers those requirements with a proven electrical profile, recognized package style, and broad application flexibility.

As part of a trusted semiconductor portfolio, this transistor supports efficient BOM planning for customers seeking stable discrete semiconductor solutions. Whether you are designing new control hardware, maintaining existing field systems, or sourcing standard-purpose components for recurring production demand, the 2N3904BU provides a dependable answer for general-purpose NPN transistor requirements.

Conclusion

The onsemi 2N3904BU is a dependable NPN BJT for engineers and procurement teams seeking a compact, through-hole transistor for amplification and switching tasks. With 40 V collector-emitter voltage, 200 mA current handling, 300 MHz transition frequency, and TO-92-3 packaging, it delivers the mix of flexibility, familiarity, and performance that B2B customers need for modern production as well as legacy support. For applications requiring a reliable general-purpose transistor from a recognized manufacturer, the 2N3904BU remains a strong and practical choice.