BD439 NPN Transistor Pinout Datasheet

Introduction

The BD439 is a medium-power NPN silicon transistor, designed for both switching and linear amplifier applications. It belongs to a family of plastic-package power transistors (e.g. BD439, BD441) used widely in audio, power supply, and driver circuits. The BD439 is suited for designs where moderate currents and voltages are present and where symmetrical or complementary operation may be needed with a PNP counterpart.

Housed in a TO-126 / SOT-32 plastic package, the BD439 offers a compact footprint and a design amenable to modest heatsinking. Its structure and doping deliver balanced performance in gain, saturation, and thermal stability for medium-power roles.

BD439 NPN Transistor

In circuits, the BD439 is frequently used in audio amplifier output stages, push-pull complementary configurations, power supply switching, and general-purpose driver circuits. Its moderate voltage rating and current capacity make it a reliable choice when paired with a PNP complement to yield symmetrical behavior.

Pinout of BD439

Key Features

• NPN polarity for positive-side or low-side conduction
• Designed for complementary pairing with PNP devices
• Compact plastic package with support for moderate heatsinking
• Balanced design for both linear amplification and switching
• Stable performance under moderate thermal loads
• Suitable for audio, driver, and general power circuits

Specifications/Characteristics

• Collector-Base Breakdown Voltage, VCBO = 60 V
• Collector-Emitter Breakdown Voltage, VCEO = 60 V
• Emitter-Base Breakdown Voltage, VEBO = 5 V
• Continuous Collector Current, IC = 4 A
• Peak (Pulsed) Collector Current, ICM = 7 A
• Collector Power Dissipation, Ptot = 36 W (at case temperature = 25 °C)
• Maximum Junction Temperature, Tj = 150 °C
• Storage Temperature Range, Tstg = –65 to +150 °C
• Collector Cut-Off Current (ICBO) ≤ 100 µA
• Emitter Cut-Off Current (IEBO) ≤ 1 mA
• DC Current Gain (hFE) minimum ~25 (under moderate conditions)
• Transition Frequency, fT = 3 MHz

Pin Configuration

Comparison BD439 (NPN) vs BD440 (PNP Complementary)

• BD439 is the NPN transistor of the complement pair, conducting during positive excursions or as the low-side device in push-pull amplifier circuits.
• BD440 is the PNP counterpart, conducting during negative excursions or acting as the high-side device in complementary amplifier or switching circuits.
• When used together, BD439 and BD440 are matched in current rating, power dissipation, and gain/frequency characteristics (with opposite polarity), enabling symmetrical push-pull behavior and minimizing distortion in amplifier outputs.

More Circuit Layouts

Key Applications of BD439 NPN Transistor

• Audio amplifier output and driver stages
• Push-pull complementary amplifier circuits
• Power supply switching and regulation
• Driver stages in control electronics
• General-purpose medium-power switching and amplification

PNP Complimentary Transistor

• The PNP complementary device to BD439 is BD440

Equivalent Transistors of BD439 NPN Transistor

Possible equivalents or alternative NPN transistors to BD439 include:

• BD441 (higher-voltage sibling in the same family)
• Other medium-power NPN transistors with similar ratings, e.g. in TO-126 / TO-220 packages with ~60 V, 4 A capacity
• General-purpose power BJTs in the same class (depending on voltage / current needs)
• If necessary, using a transistor with somewhat higher voltage margin and derating for stability

(Pin configuration of some transistors mentioned here may different from BD439).

Datasheet of BD439 NPN Transistor

Click the following Button to download the datasheet of BD439 Transistor :

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