onsemi BDX34BTSTU

Overview

BDX34BTSTU from ON Semiconductor is a PNP epitaxial silicon Darlington transistor in TO-220 package, rated for -80 V V_CEO, -10 A continuous collector current, 70 W power dissipation at T_C = 25°C, and minimum DC current gain (h_FE) of 750 at I_C = -3 A. It serves as a high-gain power switching or linear amplification device in motor control, power supply regulation, and industrial relay drivers.

For engineers reviewing the BDX34BTSTU datasheet, pinout, applications, or equivalent options, key selection criteria include its -80 V blocking capability, Darlington architecture enabling low base drive requirements, TO-220 thermal performance, and complementary pairing with BDX33B for push-pull output stages.

Technical Context

The BDX34BTSTU implements a monolithic PNP Darlington configuration with integrated emitter-base shunt resistor, delivering high current gain while maintaining robust secondary breakdown immunity. Its safe operating area (SOA) supports both continuous and pulsed operation up to -15 A peak, with V_CE(sat) ≤ -2.5 V at I_C = -3 A and I_B = -6 mA.

Designed for linear and switching applications, it features low leakage (I_CEO ≤ -0.5 mA at V_CE = -40 V), stable junction temperature operation up to 150°C, and a complementary V_CEO/V_CBO rating of -80 V - matching the BDX33B NPN counterpart for balanced dual-polarity designs.

Key Specifications

Pinout & Package

BDX34BTSTU uses the standard TO-220 package with vertical mounting orientation, metal tab electrically connected to collector, and integral mounting hole for mechanical fixation and thermal interface.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP Darlington transistor applications.

Compared with BDX34BTSTU, BDX34BRLG offers identical performance with RoHS compliance, while MJ15024G trades integration and footprint for higher voltage/power capability-making BDX34BTSTU optimal for space-constrained, medium-power industrial switching where Darlington simplicity matters.

Availability

BDX34BTSTU is available at Aetrix Electronics and suitable for industrial motor control, linear power regulation, and relay/solenoid driving applications requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for BDX34BTSTU 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 energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BDX34BTSTU belongs to ON Semiconductor's legacy power bipolar transistor family, originally developed by Fairchild for robust, high-current linear and switching applications in industrial automation and power conversion systems.

FAQ

What is the maximum continuous collector current rating for BDX34BTSTU?

The BDX34BTSTU has a maximum continuous collector current (I_C) rating of -10 A at case temperature T_C = 25°C. This rating assumes adequate heatsinking; derating is required above 25°C per the published power derating curve (Fig.6). At T_C = 100°C, the usable I_C drops to approximately -4.5 A. The BDX34BTSTU also supports -15 A pulsed collector current (I_CP) under specified test conditions (PW = 300 µs, duty cycle = 1.5%).

Is BDX34BTSTU pin-compatible with BDX34B or BDX34C variants?

Yes, BDX34BTSTU shares identical TO-220 pinout (Base–Collector–Emitter) and mechanical dimensions with all BDX34x variants including BDX34B and BDX34C. However, electrical differences exist: BDX34BTSTU is rated for -80 V V_CEO, matching BDX34B, whereas BDX34C is rated for -100 V. Substituting BDX34C may be acceptable in designs with margin, but BDX34BTSTU must not replace BDX34 or BDX34A (-45 V/-60 V) in higher-voltage applications.

Does BDX34BTSTU include an internal base-emitter shunt resistor?

No, the BDX34BTSTU does not integrate a base-emitter shunt resistor. Unlike some Darlington transistors (e.g., MPSA13), it relies on external base termination for turn-off assurance. Designers must provide a dedicated base-emitter discharge path-typically a 1–10 kΩ resistor-to ensure clean switching and prevent unintended conduction due to leakage or noise. This is confirmed by the absence of R_BE in the BDX34BTSTU datasheet's characteristic tables.

What is the typical V_CE(sat) of BDX34BTSTU under standard operating conditions?

The typical V_CE(sat) of BDX34BTSTU is -2.5 V at I_C = -3 A and I_B = -6 mA, as specified in the Electrical Characteristics table. This value represents worst-case conduction loss under defined test conditions; actual measured values may be lower (e.g., -2.2 V) depending on junction temperature and manufacturing lot. For thermal design, use -2.5 V to calculate worst-case power dissipation: P_sat = |V_CE(sat) × I_C| ≈ 7.5 W at 3 A.

Can BDX34BTSTU be used as a direct replacement for older Fairchild BDX34B parts?

Yes, BDX34BTSTU is the ON Semiconductor–branded successor to the Fairchild BDX34B, retaining identical electrical specifications, TO-220 package, pinout, and thermal characteristics. The "TSTU" suffix denotes tape-and-reel packaging per ON Semiconductor's updated nomenclature (replacing underscores with dashes post-Fairchild integration). No schematic or layout changes are needed when migrating from legacy Fairchild BDX34B to BDX34BTSTU.