BD243 NPN Transistor Pinout Datasheet

Introduction

The BD243 (and its variants BD243A, BD243B, BD243C) is a silicon epitaxial-base NPN power transistor intended for medium-power switching and linear amplification applications. It is built to handle higher voltage and current stresses, making it suitable in amplifier output stages, power supplies, and driver circuits where robustness is required. The transistor is packaged in the TO-220 plastic case, allowing effective heat sinking and mechanical stability.

Manufacturers often describe the BD243 series as designed for general-purpose amplifier and switching use, especially in circuits needing matching PNP complements (such as BD244). Its rating flexibility (via A, B, C variants) allows designers to choose suitable voltage margins depending on supply rails and transient conditions.

BD243 NPN Transistor

In real circuits, engineers employ BD243 for tasks like audio output drivers, complementary push-pull amplifiers, power regulator stages, and switching circuits where a higher-voltage NPN device is needed. Its ability to deliver decent current and power (while balancing thermal limits) makes it a versatile option in many medium-power designs.

Pinout of BD243

Key Features

• Multiple voltage variants (A, B, C) for design flexibility
• High current capacity in medium-power class
• Compatible for complementary pairing with PNP devices
• Good thermal performance when mounted on heatsinks
• Balanced trade-off between voltage, current, and gain
• Suitable for both analog amplification and switching roles

Specifications/Characteristics

• Collector-Emitter Voltage (VCEO) = 45 V for BD243 (and 60 V / 80 V / 100 V for variants)
• Collector-Emitter Voltage with base open (sustaining), VCER = 55 V for BD243 (and up to 115 V for variants)
• Collector-Base Voltage (VCBO) = 80 V for BD243B / up to 100 V for BD243C
• Emitter-Base Breakdown Voltage (VEBO) = 5 V
• Continuous Collector Current (IC) = 6 A
• Peak (Pulsed) Collector Current (ICM) = 10 A
• Base Current (IB) = 2 A (absolute maximum)
• Total Power Dissipation, Ptot = 65 W (at case temperature 25 °C)
• Operating Junction & Storage Temperature Range, TJ, Tstg = –65 to +150 °C
• Collector-Emitter Saturation Voltage (VCE(sat)) ≤ 1.5 V (at given test currents)
• Base-Emitter On Voltage (VBE(on)) up to 2.0 V (under some conditions)
• DC Current Gain (hFE) = 30 (at IC = 0.3 A)
• DC Current Gain (hFE) = 15 (at IC = 3 A)
• Thermal Resistance, Junction-to-Case, θJC = 1.92 °C/W

Pin Configuration

Comparison BD239 vs BD241 vs BD243

• BD239 is a moderate-voltage NPN transistor, typically rated for 100 V collector-emitter, used in general-purpose amplifier and switching tasks where high voltage stress is moderate.
• BD241 offers variants (60 V, 80 V, 100 V) giving designers flexibility to match voltage requirements in circuits of varying supply rails while maintaining strong current and power capabilities.
• BD243 represents the higher-voltage side in the series, often available in versions up to 100 V or more in collector-emitter and collector-base voltage ratings. It is used when voltage margin is critical in amplifier and switching designs.
• All three transistors BD239, BD241, BD243 are used for medium-power tasks and share comparable continuous current capabilities (in the ampere range) and application roles. Their main differentiation lies in how much voltage stress each can tolerate: choose BD239 when moderate margin suffices, BD241 for flexible mid-range designs, and BD243 when you need maximum voltage robustness.

More Circuit Layouts

Key Applications of BD243 NPN Transistor

• Amplifier output stages (especially in complementary designs)
• Switching regulators and power supplies
• Driver circuits for motors, relays, and power elements
• General-purpose medium-power switching tasks
• Audio amplification and signal processing circuits

PNP Complimentary Transistor

• The PNP complementary device to BD243 is BD244 (specifically matching variant BD244B / BD244C)

Equivalent Transistors of BD243 NPN Transistor

Some alternative or equivalent NPN transistors to the BD243 include:

• BD241 / BD239 (lower or moderate voltage versions in same family)
• 2N3055 (for higher power needs)
• TIP41 (for mid-power applications)
• MJL / MJE series mid-power NPN transistors
• Other NPN power transistors in TO-220 package with similar voltage/current specs

(Pin configuration of some transistors mentioned here may different from BD243).

Datasheet of BD243 NPN Transistor

Click the following Button to download the datasheet of BD243 Transistor :

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