PNP Power Transistor – BD140

🛠️ PNP Power Transistor – BD140 (TO‑126)

Overview

The BD140 is a reliable medium-power PNP transistor in a TO‑126 package, well-suited for applications like audio amplifiers, motor drivers, voltage regulation, and general switching tasks. It’s the complementary PNP counterpart to the BD139 and is frequently used in push-pull amplifier stages.

Key Features

• PNP transistor capable of 1.5 A continuous and 3 A pulsed current

• Collector-emitter voltage rating of up to 80 V (VCBO up to 100 V)

• Maximum power dissipation: 12.5 W (with heatsink) or 1.25 W at room temperature

• DC current gain (hFE) range: 40–250, depending on operating current

• Frequency response up to approx. 190 MHz

• TO‑126 package with a metal tab (collector) – easy mounting and heat dissipation

Pinout (Front view, flat face toward you):

1. Emitter

2. Collector (tab)

3. Base

• PNP logic is inverted (LOW turns transistor ON)

• Include a flyback diode for inductive loads

• Use a heatsink on the tab if dissipating significant power

Applications

• Audio amplifier driver stages

• High-current relay or motor switches

• Voltage regulation and quasi-complementary power outputs

• LED drivers and general load switching under ~1.5 A

• Push-pull stages paired with NPN transistors (e.g., BD139)

✅ Resources

1. 📄 Datasheet: BD140 PNP Power Transistor Datasheet PDF (STMotorola/Onsemi)

2. 🎥 YouTube Tutorial: “BD139 & BD140 Power Transistor Tutorial” – covers basics, wiring, and Arduino switching examples electroduino.com+3youtube.com+3hackaday.io+3