2N3904 NPN TRANSISTOR

The 2N3904 is one of the most popular and widely used NPN bipolar junction transistors (BJT) in the electronics world. Originally designed by Motorola, it has become an industry-standard component for low-power switching and small-signal amplification applications. Its combination of high current gain, fast switching speed, and very low cost has made it a go-to choice for both professional engineers and electronics hobbyists for decades. Packaged in the compact TO-92 plastic case with three leads (Emitter, Base, Collector), the 2N3904 is breadboard-friendly and ideal for through-hole prototyping. It can handle a maximum collector current of 200 mA and operate at voltages up to 40 V (V_CE) , making it suitable for driving small loads such as LEDs, relays, small motors, and logic-level signals . The transistor offers a typical DC current gain (hFE) between 100 and 300 , with a transition frequency (fT) of 300 MHz , making it equally effective in audio amplification stages, oscillators, and high-speed digital switching. As a complementary pair to the 2N3906 (PNP) , it is commonly used in push-pull amplifier stages and bidirectional switching circuits. Whether you're building your first transistor circuit on a breadboard or designing a compact production board, the 2N3904 delivers reliable, predictable performance for a vast range of small-signal applications. Specifications Part Number: 2N3904 Transistor Type: NPN Bipolar Junction Transistor (BJT) Collector-Emitter Voltage (V_CEO): 40 V Collector-Base Voltage (V_CBO): 60 V Emitter-Base Voltage (V_EBO): 6 V Maximum Collector Current (I_C): 200 mA Power Dissipation (P_D): 625 mW DC Current Gain (hFE): 100 – 300 (typical) Transition Frequency (fT): 300 MHz Operating Temperature Range: ?55°C to +150°C Package: TO-92 (through-hole) Pin Configuration: Emitter – Base – Collector (EBC, flat side facing you) Complementary PNP: 2N3906 Applications General-Purpose Switching Circuits Small-Signal Audio Amplifiers and preamp stages LED Driver Circuits for low-current LEDs Relay Driver Circuits (for small relays) Logic Level Shifters and interface circuits Oscillators and Multivibrators Pulse and Square-Wave Generators Sensor Signal Amplification Microcontroller Output Buffers (Arduino, PIC, AVR projects) Educational Electronics Kits and lab experiments DIY Hobby Projects and breadboard prototyping Push-Pull Amplifier Stages (paired with 2N3906 PNP)