STMicroelectronics BD535

Overview

BD535 from STMicroelectronics is an NPN silicon power transistor in TO-220 package, designed for medium-power linear and switching applications. It features 60 V collector-emitter sustaining voltage (VCEO(sus)), 8 A continuous collector current (IC), 50 W total dissipation at Tcase = 25°C, and DC current gain (hFE) of 20–40 at IC = 10 mA / VCE = 5 V. It is used in industrial motor control drivers and DC-DC converter output stages.

For engineers reviewing the BD535 datasheet, BD535 pinout, BD535 application, or BD535 equivalent, key selection criteria include its 60 V VCEO(sus), low 0.8 V VCE(sat) at IC = 2 A / IB = 0.2 A, 150 °C max junction temperature, TO-220 thermal interface capability, and complementary pairing with BD536 PNP for push-pull output stages.

Technical Context

The BD535 operates as a high-gain, low-saturation-voltage NPN bipolar junction transistor fabricated using Planar technology with "Base Island" layout. Its design emphasizes high hFE (20–40 at low current, 15–25 at IC = 2 A) and low VCE(sat) (0.8 V at IC = 2 A / IB = 0.2 A), enabling efficient operation in linear regulators and Class AB amplifier outputs.

It supports safe operating area (SOA) up to 8 A and 60 V under pulsed conditions, with derating beginning above 25°C case temperature. The device is rated for storage from –65 °C to +150 °C and requires heatsinking for sustained >1 A operation due to its 50 W PTOT at Tcase = 25°C.

Key Specifications

Pinout & Package

BD535 is housed in a standard TO-220 package with three leads: Collector (tab-connected), Base, and Emitter. The metal tab is electrically connected to the collector and must be isolated from chassis unless circuit topology permits common-collector configuration.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD127 and TIP31C, BD535 offers superior continuous current handling (8 A vs. 4 A / 3 A) and higher power dissipation (50 W vs. 30 W / 40 W), making it preferred for industrial motor drivers and linear regulators requiring sustained >4 A output.

Availability

BD535 is available at Aetrix Electronics and suitable for industrial motor drivers, linear voltage regulators, DC-DC converter outputs, and audio power amplifier outputs requiring stable component supply across production lifecycles.

Supply support for BD535 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, designing and manufacturing analog, digital, and mixed-signal ICs and discrete devices for industrial, automotive, and consumer markets.

BD535 belongs to ST's legacy power bipolar transistor family, engineered for robustness and thermal reliability in medium-power linear and switching applications where cost-effective discrete solutions are required.

FAQ

Is BD535 pin-compatible with BD533 or BD537?

No. While all three share the TO-220 package and pinout (C-B-E), BD535 has distinct absolute ratings: 60 V VCEO(sus) and 8 A IC, versus 45 V / 8 A for BD533 and 80 V / 8 A for BD537. Electrical characteristics-including hFE and VCE(sat)-are optimized per voltage grade, so direct substitution without circuit revalidation is not advised.

Does BD535 require a heatsink in all applications?

Yes, for any continuous operation above ~1 A or pulsed operation exceeding 10 W average power. With PTOT = 50 W at Tcase = 25°C and thermal resistance RθJC ≈ 0.5 °C/W (inferred from TO-220 mechanical data), even moderate loads generate significant junction temperature rise without heatsinking-especially above ambient temperatures of 40 °C.

Can BD535 be used in avalanche mode?

No. BD535 is not rated or characterized for controlled avalanche operation. Its VCEO(sus) = 60 V is a sustaining voltage under specified pulsed test conditions-not an avalanche breakdown rating. Operating beyond VCEO risks secondary breakdown and irreversible damage; external clamping or snubbing is required for inductive switching.

What is the meaning of "Base Island" layout in BD535's construction?

The "Base Island" layout is a proprietary Planar process technique where the base region is formed as an isolated, uniformly doped island within the epitaxial collector. This improves hFE consistency, reduces base spreading resistance, and lowers VCE(sat) by minimizing lateral current flow-key to BD535's high gain and low saturation performance at high current densities.