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BD140 PNP Medium Power Transistor

Specification	Details
Transistor Type	PNP (Bipolar Junction Transistor)
Package Type	SOT-32 / TO-126
Max Collector Current ($I_C$)	-1.5 Amps
Max Collector-Emitter Voltage ($V_{CEO}$)	-80 Volts
Max Collector-Base Voltage ($V_{CBO}$)	-80 Volts
DC Current Gain ($h_{FE}$)	40 to 250
Max Power Dissipation ($P_{tot}$)	12.5 Watts (with Heat Sink)
Operating Temperature	-55°C to +150°C

Price

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₹ 4.24

(Tax included)

Product Description

The BD140 is a widely used PNP medium power transistor, serving as the essential complementary partner to the NPN BD139. Housed in the versatile TO-126 package, it is designed for high-side switching and audio amplification. With the capability to handle up to 1.5A of continuous current and a breakdown voltage of 80V, it is a robust choice for driving medium-sized loads such as solenoids, motors, and high-brightness LED arrays. Its linear gain characteristics also make it a staple in the output stages of Class AB audio amplifiers, where it works in tandem with its NPN counterpart to provide balanced signal reproduction.

Key Features

PNP Configuration: Ideal for high-side switching applications where the load is connected between the collector and ground.
Complementary Pairing: Specifically matched to work with the BD139 (NPN) for push-pull amplifier topologies.
High Voltage Tolerance: Rated at 80V, providing a reliable safety margin for 24V and 48V DC systems.
Flexible Mounting: The TO-126 package includes a center hole for easy attachment to aluminum heat sinks or chassis.
High Thermal Stability: Maintains consistent performance over a wide temperature range, essential for industrial control boards.
Low Saturation Voltage: Ensures efficient power transfer with minimal energy lost as heat when fully switched on.

Technical Details

Pin 1: Emitter
Pin 2: Collector
Pin 3: Base
Mounting Hole: Fits M3 size screws.

Prototyping and Engineering Tips from Robogears

Pinout Identification: CRITICAL: Looking at the front of the transistor (where the text is printed) with the pins pointing downward, the pinout is Emitter (1), Collector (2), Base (3). Note that the metal tab on the back is also connected to the Collector (Pin 2).
PNP Switching Logic: Remember that for a PNP transistor to conduct, the Base must be at a lower potential than the Emitter. In a 12V circuit, if the Emitter is at 12V, the transistor will turn ON when the Base voltage drops (usually through a resistor to ground or a microcontroller pin).
Thermal Management: If you are drawing more than 200-300mA, the BD140 will generate heat. To reach the 12.5W rating, you must use a heat sink. When mounting, use a mica insulator and a plastic washer if your heat sink is grounded, as the collector is electrically "live" on the transistor's metal tab.
Audio Amplifier Usage: In push-pull audio circuits, the BD139 and BD140 are often used together. To ensure thermal stability, mount both transistors on the same heat sink. This helps the transistors track temperature changes together, preventing "thermal runaway" that could lead to distortion or circuit failure.
Inductive Snubbing: If using this PNP transistor to switch high-side inductive loads (like a relay or motor), always place a Flyback Diode across the load. The anode should go to the collector side and the cathode to the positive supply rail to safely dissipate the reverse voltage spike.

Package Includes

1 x BD140 PNP Medium Power Transistor

Disclaimer: Product images are shown for illustrative purposes only. The branding (ST, ON Semi, etc.) or specific "gain group" marking (e.g., -10 or -16) may vary between batches, but all technical specifications and 1.5A/80V performance standards remain as described.

Safety Warning: Power transistors can become extremely hot during operation. Do not touch the component or the heat sink while the circuit is powered. Ensure all connections are secure, as a loose base wire can cause the transistor to stay partially ON, leading to rapid overheating and failure.