BD139 NPN 80V 1.5A Bipolar Transistor TO-126

BD139 NPN 80V 1.5A Bi-polar Transistor TO-126 is a versatile, medium-power NPN silicon epitaxial planar transistor specifically designed for general-purpose switching and amplifier applications. With a robust collector-emitter voltage (V_CEO) of 80V and continuous collector current (I_C) capability up to 1.5A, the BD139 provides reliable performance in intermediate power stages. Therefore, engineers commonly utilize this transistor in systems that require reliable current amplification or fast switching of moderate loads. Furthermore, its complementary nature to the BD140 (PNP) simplifies the design of push-pull amplifier circuits. The compact, insulated TO-126 package allows for efficient heat dissipation, making it ideal for continuous operation in consumer electronics and industrial equipment.

Key Features:

• Medium Power Handling: The transistor supports a continuous collector current (I_C) of 1.5A, which is suitable for driving relays, LEDs, and small motors.
• High Voltage Rating: Features a Collector-Emitter Voltage (V_CEO) of 80V, consequently allowing its use in higher-voltage circuits than standard small-signal transistors.
• High Current Gain (h_FE): Offers a high DC current gain range, ensuring efficient operation and easy driving from low-power control circuitry.
• TO-126 Insulated Package: This small, molded package simplifies mounting onto heat sinks when necessary, promoting effective thermal management.
• Complementary to BD140: You can easily pair the NPN BD139 with the PNP BD140 for symmetrical or complementary output stage designs, for instance in audio amplifiers.

Technical Specifications:

• Transistor Type: NPN Bi-polar Junction Transistor (BJT)
• Collector-Emitter Voltage (V_CEO): 80 V max
• Collector-Base Voltage (V_CBO): 80 V max
• Emitter-Base Voltage (V_EBO): 5 V max
• Continuous Collector Current (I_C): 1.5 A max
• Total Power Dissipation (P_tot): 12.5 W max at T_c = 25°C
• DC Current Gain (h_FE): 40 to 250 (Typically tested at I_C=150mA, V_CE=2V)
• Transition Frequency (f_T): 190 MHz (High frequency allows for fast switching)
• Operating Junction Temperature (T_j): −65°C to +150°C

Mechanical Specifications:

• Package Style: TO-126 (SOT-32)
• Mounting: Through-Hole (THT)
• Leads: Three leads (Emitter, Collector, Base)
• Thermal Resistance (R_thj-c): Max 10 °C/W (Junction-to-Case)

Dimensions:

• Body Width: ≈ 7.8 mm
• Body Height (excluding lead): ≈ 10.7 mm
• Pin Pitch: 2.3 mm (E-C spacing) / 2.3 mm (C-B spacing)
• Lead Length: ≈ 13.5 mm
• Hole Diameter (for screw mounting): ≈ 3.0 mm (Often used for securing to a heat sink)

Pinout and Wiring:

• Pin 1 (E): Emitter. Connect this to the ground reference or the return path for the output current.
• Pin 2 (C): Collector. Connect this to the positive supply rail (V_CC) via the load.
• Pin 3 (B): Base. Apply the control signal/current to this pin to turn the transistor ON.
• Wiring Note: Always ensure you apply a current-limiting resistor to the Base pin to safely control the collector current, otherwise you risk damaging the transistor.

Datasheet Reference:

• Download STMicroelectronics BD139 Datasheet

Commonly Used in:

• Driver Stages: Serves as a pre-driver or output driver for higher-power transistors (like TIP series) in power supplies.
• Audio Amplifiers: Used in the output stages of Class B and Class AB audio amplifiers, especially those with low to medium power output.
• Industrial Control: Acts as a switching element for industrial solenoids, relays, and indicator lamps.

Applications:

• Switching Power Supplies: Designers utilize it for various non-critical switching functions within power circuits.
• LED Strip Drivers: In addition, it handles the current switching for controlling moderate to high-power LED arrays.
• Series Voltage Regulators: Functions as the pass transistor in basic linear voltage regulation circuits.
• Motor Control: Drives small DC motors or stepping motor windings in low-power robotics and automation.

Equivalent Models:

• BD137, BD135: Lower voltage rating alternatives (60V and 45V, respectively) within the same family and package, often interchangeable in low-voltage applications.
• BC639: A lower current but functionally similar NPN transistor that engineers sometimes substitute in lighter-duty applications.
• BD237, BD239: Higher power TO-225 package alternatives that offer similar characteristics but increased current capability.

Package Includes:

• 1 x BD139 NPN 80V 1.5A Bi-polar Transistor TO-126