onsemi 2N3904CBU

Overview

2N3904CBU from ON Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for amplification and switching in low-power analog and digital circuits. It delivers DC current gain (h_FE) of 70–300 at I_C = 1.0 mA, supports 100 MHz current-gain bandwidth (f_T), withstands V_CEO = 40 V, and operates across −55 °C to +150 °C - commonly used in signal conditioning stages of sensor interfaces and discrete logic level translation.

For engineers reviewing the 2N3904CBU datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CE(sat) ≤ 0.3 V at I_C = 50 mA/I_B = 5 mA, thermal resistance R_θJA = 200 °C/W in TO-92, noise figure NF = 5.0 dB at 10 Hz–15.7 kHz, and guaranteed EBC pinout alignment with JEDEC TO-92 3L mechanical standard.

Technical Context

The 2N3904CBU operates as a single NPN silicon BJT with fixed emitter-base and collector-base junction structures optimized for linear amplification and saturated switching. Its f_T = 300 MHz enables RF-capable small-signal gain up to VHF band, while its C_obo = 4.0 pF and C_ibo = 8.0 pF support stable high-frequency biasing without external neutralization.

It uses standard base-emitter forward biasing (V_BE(sat) = 0.65–0.95 V) and collector-emitter saturation (V_CE(sat) = 0.2–0.3 V) to achieve fast switching with t_d/t_r = 35 ns and t_f = 50 ns under defined test conditions (V_CC = 3.0 V, I_C = 10 mA, I_B1 = I_B2 = 1.0 mA).

Key Specifications

Pinout & Package

2N3904CBU is housed in a through-hole TO-92 3L package per JEDEC TO-226AA, with standardized lead spacing (0.100″ pitch), molded epoxy body, and EBC terminal sequence confirmed by Fairchild/ON Semiconductor mechanical drawings and marking diagrams.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN general-purpose amplifier applications.

Compared with MMBT3904 and PN2222A, the 2N3904CBU offers optimal balance of through-hole manufacturability, thermal margin (625 mW P_D), and proven EBC pinout consistency - making it preferred for lab validation, education kits, and low-volume industrial controls where layout flexibility and thermal headroom are prioritized.

Availability

2N3904CBU is available at Aetrix Electronics and suitable for audio pre-amplifier stages, microcontroller GPIO level shifters, and LED driver circuits requiring stable component supply and long-term obsolescence management.

Supply support for 2N3904CBU includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

ON Semiconductor is a global semiconductor manufacturer specializing in power management, analog, sensor, and discrete solutions for automotive, industrial, and cloud infrastructure markets.

The 2N3904CBU belongs to ON Semiconductor's legacy general-purpose transistor product line, originally developed by Fairchild and maintained for broad compatibility in educational, prototyping, and cost-sensitive industrial applications.

FAQ

What is the maximum collector current rating for the 2N3904CBU?

The 2N3904CBU has a continuous collector current rating (I_C) of 200 mA per Absolute Maximum Ratings. This value is valid at T_A = 25 °C and must be derated linearly above 25 °C using the specified 5.0 mW/°C thermal derating factor. Exceeding this limit risks permanent degradation of h_FE and increased V_CE(sat). The 2N3904CBU is not rated for pulsed operation beyond datasheet-defined test conditions without consultation with ON Semiconductor.

Does the 2N3904CBU have a documented pinout configuration?

Yes, the 2N3904CBU uses the standard EBC (Emitter-Base-Collector) pinout for TO-92 3L packages, confirmed by Fairchild/ON Semiconductor mechanical drawings and marking diagrams. When viewed with flat side facing outward and leads pointing downward, the left-to-right pin order is E-B-C. This matches JEDEC TO-226AA specification and is electrically identical to the 2N3904TA and 2N3904TF variants. The 2N3904CBU pinout is not ECB or CBE.

What is the typical noise figure of the 2N3904CBU and under what conditions is it measured?

The 2N3904CBU has a typical noise figure (NF) of 5.0 dB, measured at I_C = 100 μA, V_CE = 5.0 V, R_S = 1.0 kΩ, and frequency range 10 Hz to 15.7 kHz. This value reflects performance in low-frequency small-signal amplification and is validated per the original Fairchild test methodology. The 2N3904CBU noise figure remains stable across −40 °C to +125 °C ambient, supporting consistent audio and sensor interface behavior without recalibration.

Can the 2N3904CBU be used in RF amplifier applications?

Yes, the 2N3904CBU supports RF amplifier applications up to 100 MHz due to its f_T = 300 MHz and low parasitic capacitances (C_obo = 4.0 pF, C_ibo = 8.0 pF). It is commonly deployed in VHF receiver front-ends, crystal oscillator buffers, and low-power transmitter driver stages. However, the 2N3904CBU requires external impedance matching networks and bias stabilization for stable RF operation, and its gain flatness degrades above 150 MHz - so it is not recommended for UHF or microwave designs. The 2N3904CBU remains effective in sub-200 MHz discrete RF functions.

How does the thermal performance of the 2N3904CBU compare to SMT alternatives like MMBT3904?

The 2N3904CBU has R_θJA = 200 °C/W in TO-92, significantly better than the MMBT3904's R_θJA = 357 °C/W in SOT-23. This means the 2N3904CBU can dissipate more power before reaching 150 °C junction temperature under identical ambient conditions - e.g., at 70 °C ambient, the 2N3904CBU supports ~400 mW versus ~220 mW for MMBT3904. The 2N3904CBU's superior thermal margin makes it preferable for thermally constrained through-hole designs where airflow is limited.