BD437 NPN Transistor Pinout Datasheet

Introduction

The BD437 is a medium-power NPN silicon transistor designed for both switching and linear amplifier applications. It is part of the STMicroelectronics BD43x series of complementary power transistors. ST describes it as a silicon epitaxial-base NPN transistor in JEDEC SOT-32 plastic packaging, intended for medium power linear and switching use.

Because it belongs to a family with matched PNP complements (BD438), BD437 is commonly used in push-pull amplifier stages, audio output circuits, and general-purpose power switching applications. Its matching with a PNP partner helps designers maintain symmetry in gain and distortion in amplifier outputs.

BD437 NPN Transistor

In practical circuits, BD437 finds application in audio drivers, small power supplies, and general electronics where moderate current and voltage levels are required. Its robustness and availability make it a good choice when a transistor above BD435 is needed for a bit more voltage margin.

Pinout of BD437

Key Features

• Enhanced voltage capability within the BD43x transistor family
• Balanced design for linear and switching operation
• Compatibility with complementary PNP devices (for push-pull designs)
• Plastic package amenable to moderate heat dissipation
• Stable performance in amplifier and driver circuits
• Good availability as a mid-class power transistor

Specifications/Characteristics

• Collector-Base Breakdown Voltage, VCBO = 32 V
• Collector-Emitter Breakdown Voltage, VCEO (or equivalently VCES with base open) = 32 V
• Emitter-Base Breakdown Voltage, VEBO = 5 V
• Continuous Collector Current, IC = 4 A
• Peak (Pulse) Collector Current, ICM = 7 A
• Base Current, IB = 1 A (maximum)
• Total Power Dissipation, Ptot = 36 W (case temperature = 25 °C)
• Maximum Junction Temperature, Tj = 150 °C
• Storage Temperature Range, Tstg = –65 to +150 °C
• DC Current Gain, hFE (typical) ~ 40 (under moderate conditions)
• Collector-Emitter Saturation Voltage, VCE(sat) = ~0.5 V (for IC = 2 A, IB = 0.2 A)

Pin Configuration

Comparison BD437 (NPN) vs BD438 (PNP Complementary)

• BD437 is the NPN side of the complementary pair, conducting on positive halves of push-pull output cycles and acting as the lower-side (or negative switching) device in many amplifier or switching circuits.
• BD438 is its PNP counterpart, conducting on negative halves (or high-side switching) in complementary designs.
• When used together, BD437 and BD438 offer matched characteristics in gain, current handling, power dissipation, and thermal behavior, enabling symmetrical operation in push-pull amplifiers or other matched circuits. Their polarity difference is the key distinction, but their electrical specs are designed to pair well in complementary roles.

More Circuit Layouts

Key Applications of BD437 NPN Transistor

• Audio amplifier output and driver stages
• Push-pull complementary amplifier topologies
• Switching regulators and power supply circuits
• General-purpose medium-power switching roles
• Driver transistors in power control circuits

PNP Complimentary Transistor

• The PNP complementary device to BD437 is BD438

Equivalent Transistors of BD437 NPN Transistor

Some possible equivalents or alternative transistors include:

• BD433 (lower voltage variant within same family)
• BD437 (higher-voltage variant in the same family)
• Other NPN medium-power transistors with similar voltage/current ratings in TO-126 or TO-220 packages
• For particular use, general purpose power NPN BJTs like TIP41 or MJL series (if voltage and current needs align)

(Pin configuration of some transistors mentioned here may different from BD437).

Datasheet of BD437 NPN Transistor

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