onsemi 2N4402BU

Overview

2N4402BU from Fairchild Semiconductor is a PNP bipolar junction transistor designed for general-purpose amplification and switching in low-to-medium power circuits, with 40 V V_CEO, 600 mA continuous collector current, and TO-92 package - used in discrete logic interfaces, relay drivers, and signal-level switching in industrial control modules.

For engineers reviewing the 2N4402BU datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO/V_CBO rating symmetry, h_FE variation across I_C (20–150), V_CE(sat) at 500 mA, thermal resistance (R_θJA = 200 °C/W), and TO-92 mechanical compatibility.

Technical Context

The 2N4402BU operates as a standard PNP BJT with common-emitter configuration, supporting both linear amplification (h_FE = 30–150 at I_C = 1–500 mA) and saturated switching (V_CE(sat) ≤ 0.75 V at I_C = 500 mA, I_B = 50 mA). Its breakdown ratings (V_CEO = V_CBO = 40 V, V_EBO = 5.0 V) define safe operating limits under reverse-biased conditions.

Thermal design relies on R_θJA = 200 °C/W and R_θJC = 83.3 °C/W, with maximum junction temperature of +150 °C and storage range from –55 °C to +150 °C. Switching performance includes t_d = 15 ns, t_r = 20 ns, t_s = 225 ns, and t_f = 30 ns under pulsed test conditions (≤300 µs, ≤2% duty cycle).

Key Specifications

Pinout & Package

2N4402BU is housed in a through-hole TO-92 package with standardized lead orientation: flat side facing viewer, leads down, left-to-right pin order E-B-C (Emitter-Base-Collector). Package dimensions conform to JEDEC TO-92 outline, enabling compatibility with legacy PCB footprints and manual assembly processes.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA92 and BC557, the 2N4402BU delivers optimal balance of 40 V breakdown, 600 mA current capacity, and low V_CE(sat) - making it preferred for medium-power PNP switching where thermal management and conduction loss are critical.

Availability

2N4402BU is available at Aetrix Electronics and suitable for relay drivers, discrete logic level shifters, linear regulator pass elements, and overvoltage protection clamps requiring stable component supply and long-term obsolescence resilience.

Supply support for 2N4402BU 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The 2N4402BU belongs to Fairchild's legacy general-purpose bipolar transistor family, engineered for cost-sensitive, reliability-critical industrial and consumer applications demanding proven TO-92 performance.

FAQ

What is the maximum continuous collector current rating for the 2N4402BU?

The 2N4402BU has a maximum continuous collector current (I_C) rating of 600 mA at T_A = 25 °C. This rating must be derated linearly by 5.0 mW/°C above 25 °C ambient temperature, based on its 625 mW total power dissipation limit and thermal resistance of 200 °C/W. The 2N4402BU is commonly used at ≤500 mA to maintain safe junction temperature margins in real-world PCB layouts.

Is the 2N4402BU suitable for switching applications, and what are its key switching parameters?

Yes, the 2N4402BU is explicitly characterized for switching use, with published parameters including delay time (t_d) = 15 ns, rise time (t_r) = 20 ns, storage time (t_s) = 225 ns, and fall time (t_f) at I_C = 150 mA. These values are measured under pulsed conditions (≤300 µs, ≤2% duty cycle), confirming the 2N4402BU's suitability for medium-speed digital switching up to ~1 MHz in properly biased circuits.

What is the pin configuration of the 2N4402BU in its TO-92 package?

The 2N4402BU uses the standard TO-92 pinout: when viewing the flat side of the package with leads pointing downward, the left-to-right pin order is Emitter (E), Base (B), Collector (C). This matches JEDEC TO-92 outline specifications and ensures mechanical and electrical compatibility with legacy designs using similar PNP transistors such as the 2N3906 or BC557.

Does the 2N4402BU have documented avalanche capability or ruggedness for inductive load switching?

No, the 2N4402BU datasheet does not specify avalanche energy rating (E_AS), ruggedness curves, or SOA (Safe Operating Area) plots for inductive switching. It is rated for resistive and moderately reactive loads only. For relay or solenoid driving, external flyback diodes are mandatory. The 2N4402BU should not be relied upon for unclamped inductive turn-off stress without supplemental protection.

How does the 2N4402BU's h_FE vary with collector current and temperature?

The 2N4402BU's h_FE ranges from 30 at I_C = 1 mA to 150 at I_C = 10 mA, then decreases to 50 at I_C = 150 mA and 20 at I_C = 500 mA - indicating strong current-dependent gain compression. Temperature effects show typical h_FE increase at elevated T_A, per characteristic curves. Designers must verify bias stability across this full 20–150 range when using the 2N4402BU in linear or switching modes.