STMicroelectronics BUX10

Overview

BUX10 from STMicroelectronics is a high-power silicon NPN transistor in TO-3 metal package, designed for linear and switching applications in industrial motor control and power conversion systems. It delivers 25 A continuous collector current, 150 W total power dissipation at T_case ≤ 25 °C, 125 V V_CEO, and fast switching with t_on = 0.5–1.5 µs and t_s = 0.6–1.2 µs.

For engineers reviewing the BUX10 datasheet, BUX10 pinout, BUX10 application, or BUX10 equivalent, key selection considerations include its 200 °C maximum junction temperature, 1.17 °C/W thermal resistance (junction-to-case), second-breakdown robustness (5 A at V_CE = 30 V, 1 s), clamped inductive switching capability (20 A at V_clamp = 125 V), and DC current gain of 10–60 across 10–20 A operating range.

Technical Context

The BUX10 employs a multi-epitaxial planar structure optimized for high-current, high-voltage operation in ruggedized industrial environments. Its design supports both linear-mode amplification (e.g., Class-A/B audio or precision current sources) and hard-switching duty (e.g., relay drivers, PWM motor controllers), with built-in second-breakdown immunity and clamped inductive load handling.

It operates with V_CEX = 160 V under forced base-emitter reverse bias (V_BE = −1.5 V), enabling reliable blocking in inductive flyback scenarios. The device's f_T = 8 MHz at I_C = 1 A confirms usable RF capability up to low-MHz switching frequencies, while its V_CE(sat) = 0.3–1.2 V across 10–20 A ensures low conduction loss in power stages.

Key Specifications

Pinout & Package

Package: TO-3 metal case (Jedec standard), with collector electrically connected to the case for direct heatsink mounting and low-inductance thermal path.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-power NPN transistor applications.

Compared with 2N3055 and MJE13009, the BUX10 uniquely balances 125 V blocking, 25 A current, and 150 W dissipation in a low-R_th TO-3 package-making it optimal for 100 V-class industrial motor drives and linear supplies where both voltage headroom and thermal density matter.

Availability

BUX10 is available at Aetrix Electronics and suitable for industrial motor control, linear power regulation, switch-mode power supplies, and inductive load switching requiring stable component supply and long-term industrial lifecycle support.

Supply support for BUX10 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power discrete solutions with vertical manufacturing and broad IP portfolio.

The BUX10 belongs to ST's high-power bipolar transistor product line, engineered specifically for ruggedized linear and switching applications in military-grade and heavy-industrial equipment where reliability under thermal and electrical stress is non-negotiable.

FAQ

Is the BUX10 still in active production?

No-the BUX10 is marked "Obsolete Product(s)" in ST's official March 2003 datasheet. It remains available through authorized legacy distributors and Aetrix Electronics' long-life inventory program, with full traceability and extended lifecycle support documentation.

Can the BUX10 be used in parallel configurations?

Yes, but only with emitter-ballasting resistors (typically 0.1 Ω, 5 W) per device to ensure current sharing. Its positive temperature coefficient of V_CE(sat) supports inherent thermal stability, but mismatched h_FE and layout asymmetry require careful balancing for >50 A aggregate current.

What is the recommended heatsink interface for the TO-3 case?

A mica or silicone thermal pad (0.1–0.2 mm thick) with thermal conductivity ≥1.5 W/m·K is recommended. Direct metal-to-metal mounting is not advised due to risk of shorting the collector (case) to heatsink unless insulated hardware is used and verified for dielectric strength >500 V.

Does the BUX10 require base current limiting in switching applications?

Yes-base current must be actively limited to ≤5 A (absolute max) and typically set to 1–2 A for 10–20 A collector conduction. An external series resistor or constant-current driver is required; failure to limit IB risks permanent base-emitter junction damage during saturation.