onsemi BD37510STU

Overview

BD37510STU from Fairchild Semiconductor is an NPN epitaxial silicon transistor in TO-126 package, rated for 45 V V_CEO, 2 A continuous collector current, and 25 W power dissipation at T_C = 25°C, used in medium-power linear amplification and switching applications such as audio output stages and relay drivers.

For engineers reviewing the BD37510STU datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO = 45 V, I_C = 2 A, h_FE = 40–100 (at I_C = 0.15 A), V_CE(sat) = 1 V (at I_C = 1 A, I_B = 0.1 A), and TO-126 thermal performance with case temperature derating.

Technical Context

This NPN bipolar junction transistor operates in active, saturation, and cutoff regions with specified DC current gain (h_FE) ranging 40–100 at V_CE = 2 V, I_C = 0.15 A, and 20–375 at V_CE = 2 V, I_C = 1 A. It supports pulse operation up to I_CP = 3 A (PW = 350 µs, duty cycle = 2%).

Its safe operating area (SOA) is defined up to V_CE = 45 V and I_C = 2 A at T_C = 25°C, with thermal derating to zero power at T_C = 150°C. Junction temperature is rated to 150°C, and storage temperature spans –55°C to +150°C.

Key Specifications

Pinout & Package

BD37510STU is housed in a TO-126 plastic package with integral heat slug, designed for through-hole mounting and direct heatsink attachment. Pin 1 is Emitter, Pin 2 is Collector (connected to tab), Pin 3 is Base.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN medium-power switching and linear amplifier applications.

Compared with BD37510STU, MJD31C offers higher voltage and current headroom in TO-220 but demands more board space and thermal design effort, while BD139 matches the TO-126 form factor and pinout with slightly reduced current rating but broader h_FE range-making it viable for lower-power linear stages where gain consistency matters.

Availability

BD37510STU is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, relay interfaces, and linear regulator pass elements requiring stable component supply across industrial, instrumentation, and legacy consumer electronics programs.

Supply support for BD37510STU 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 devices before its acquisition by ON Semiconductor in 2016.

BD37510STU belongs to the BD375/377/379 family of medium-power NPN transistors designed for linear amplification and robust switching in cost-sensitive industrial and audio applications where TO-126 thermal performance and proven reliability are essential.

FAQ

What is the maximum continuous collector current for BD37510STU?

The BD37510STU has a maximum continuous collector current (I_C) of 2 A at case temperature T_C = 25°C. This rating decreases with rising case temperature per the power derating curve in the datasheet, reaching zero at T_C = 150°C. For reliable operation above 65°C, heatsinking is required. The BD37510STU must not exceed this limit in DC or high-duty-cycle applications to avoid thermal runaway or permanent damage.

Is BD37510STU pin-compatible with BD376?

No, BD37510STU is not pin-compatible with BD376. BD37510STU is an NPN transistor in TO-126 package with pinout Emitter–Collector–Base (1–2–3), while BD376 is its complementary PNP counterpart with reversed polarity and identical mechanical outline but opposite terminal assignment. Using BD37510STU in place of BD376 will result in circuit failure due to reversed current flow and incorrect biasing. Always verify polarity and pin mapping before substitution.

What is the typical DC current gain (h_FE) of BD37510STU at 1 A collector current?

At V_CE = 2 V and I_C = 1 A, the BD37510STU exhibits h_FE2 ranging from 20 to 375, depending on device classification (6, 10, 16, or 25). The minimum guaranteed value is 20, and typical units measure ~100–150. This wide spread means base drive must be designed for the minimum h_FE to ensure saturation across all BD37510STU units in production. The BD37510STU datasheet provides h_FE histograms for each classification group.

Can BD37510STU be used in switching power supplies?

BD37510STU can be used in low-frequency (<50 kHz), low-power switching applications such as offline flyback snubbers or auxiliary supplies, but it is not optimized for high-frequency SMPS. Its t_OFF = 500 ns and lack of specified switching energy parameters limit efficiency above ~100 kHz. For dedicated switching power supplies, modern MOSFETs or faster BJTs like MJD122 are preferred. The BD37510STU remains appropriate for simpler on/off control where speed is secondary to ruggedness and cost.

Does BD37510STU require a heatsink in all applications?

A heatsink is required for BD37510STU when power dissipation exceeds ~3–5 W, depending on ambient and airflow conditions. At full 2 A DC current and V_CE = 2 V, dissipation reaches 4 W-often manageable with minimal copper pour. However, at 25 W max rating, even brief operation near that level demands substantial heatsinking. The BD37510STU's TO-126 tab must be electrically isolated unless the collector node is at chassis ground. Thermal design must follow the published derating curve to maintain T_J ≤ 150°C.