onsemi 2N5401BU

Overview

2N5401BU from Fairchild Semiconductor is a PNP epitaxial silicon small-signal transistor rated for −150 V V_CEO, −600 mA I_C, 625 mW P_C, with DC current gain (h_FE) of 30–240 at I_C = −1 mA to −50 mA, and f_T up to 400 MHz - used in high-voltage amplifier and switching stages of analog signal conditioning circuits.

For engineers reviewing the 2N5401BU datasheet, pinout, applications, or equivalent options, key selection considerations include its −150 V collector-emitter breakdown rating, low saturation voltage (V_CE(sat) = −0.2 V @ I_C = −10 mA), TO-92 package compatibility, and verified noise figure of 8 dB in audio-frequency amplification.

Technical Context

This PNP bipolar junction transistor operates with reverse-polarity biasing: emitter positive relative to base and collector. Its high V_CEO (−150 V) and V_CBO (−160 V) support use in high-side switching and negative-rail amplification where voltage swing exceeds −100 V. The device exhibits h_FE variation across collector current (30 at −1 mA, 60 at −10 mA, 50 at −50 mA), indicating optimized mid-current gain behavior.

Thermal design is constrained by 625 mW maximum power dissipation and 150 °C junction temperature limit. Output capacitance (C_ob = 6 pF @ V_CB = −10 V) and f_T (100–400 MHz) confirm suitability for audio and low-MHz RF amplification, not broadband RF or switching above 10 MHz.

Key Specifications

Pinout & Package

2N5401BU is housed in a standard TO-92 plastic package with lead configuration: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (suffix "BU" denotes this pinout variant per Fairchild documentation).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP small-signal transistor applications.

Compared with MPSA92 and BC557B, the 2N5401BU offers optimal balance of −150 V capability, predictable h_FE spread, and industry-standard E-B-C pinout - making it preferred for legacy audio, industrial control, and high-side switching where voltage and gain stability are jointly critical.

Availability

2N5401BU is available at Aetrix Electronics and suitable for audio preamplifiers, high-voltage level shifters, discrete op-amp input stages, and negative linear regulator designs requiring stable component supply and long-term obsolescence management.

Supply support for 2N5401BU 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 2N5401BU belongs to Fairchild's legacy general-purpose PNP transistor product line, designed specifically for high-voltage analog signal amplification, switching, and linear regulation in industrial, audio, and instrumentation equipment.

FAQ

What is the pin configuration of the 2N5401BU?

The 2N5401BU uses TO-92 package with Emitter-Base-Collector (E-B-C) pinout: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector. This matches Fairchild's "BU" suffix designation and differs from "BL" (E-C-B) variants. Confirm orientation via flat side and lead-down view per datasheet mechanical drawing.

Does the 2N5401BU support audio-frequency amplification?

Yes, the 2N5401BU is validated for audio use: its 8 dB noise figure (10 Hz–15.7 kHz), f_T up to 400 MHz, and stable h_FE at low currents make it suitable for microphone preamps and line-level gain stages. It is commonly deployed in discrete Class-A audio circuits where low distortion and thermal stability are prioritized.

What is the maximum safe operating voltage for the 2N5401BU?

The absolute maximum collector-emitter voltage (V_CEO) for the 2N5401BU is −150 V at T_A = 25 °C. Derating is required above 25 °C per the datasheet's thermal curve; sustained operation above −120 V should include margin for transients and temperature rise to avoid avalanche breakdown.

Can the 2N5401BU replace the 2N5401 without changes?

Yes - the 2N5401BU is a direct replacement for the base 2N5401, sharing identical electrical specifications, TO-92 package, and E-B-C pinout. The "BU" suffix explicitly denotes the standard pin assignment; no PCB or schematic modifications are needed when substituting 2N5401BU for 2N5401 in existing designs.

Is the 2N5401BU suitable for switching applications?

Yes, the 2N5401BU supports switching with V_CE(sat) = −0.2 V at I_C = −10 mA and −0.5 V at I_C = −50 mA. Its 625 mW power limit and TO-92 thermal resistance (~200 °C/W) constrain duty cycle and frequency; best suited for <10 kHz, medium-current (<100 mA), high-voltage (≤−120 V) switching such as relay drivers or HV logic interfaces.