The BD139 is an NPN power transistor designed to use in audio amplifier stages and general purpose applications. It’s part of a complementary pair, with the BD140 as its PNP counterpart. The BD139 is widely used in electronic circuits due to its high current handling, decent voltage ratings and easy to use TO-126 (SOT-32) package. This will making it a popular choice among electronics hobbyists and professionals alike.
BD139 Pinout Configuration
The BD139 transistor comes in a TO-126 (SOT-32) plastic package with the following pin configuration when we viewed from the front side (The flat side facing you, pins downward),
| Pin Number | Pin Name |
|---|---|
| 1 | Base |
| 2 | Collector |
| 3 | Emitter |
BD139 Transistor Features and Specifications
- Collector-Emitter Voltage (VCEO): 80V
- Collector-Base Voltage (VCBO): 80V
- Emitter-Base Voltage (VEBO): 5V
- Collector Current (IC): 1.5A continuous, 3A peak
- Base Current (IB): 0.5A
- Total Power Dissipation: 12.5W at case temperature 25°C
- DC Current Gain (hFE): 40 to 250 depending on type (BD139-10 or BD139-16)
- Saturation Voltage VCE(sat): Typically 0.5V at IC = 0.5A
- Junction Temperature (Tj max): 150°C
BD139 Equivalent Transistors
If the BD139 transistor is not available, the following are suitable alternatives you can use,
- BD135
- TIP31
- 2N6488
- MJE182
Applications of BD139 Transistor
- Audio amplifier driver stages
- Power supply regulators
- Switching and signal amplification
- Relay drivers
- Motor drivers in low to medium power circuits
Complementary Pair
The BD140 is the PNP complement to BD139 NPN transistors, This transistors are used together in push-pull amplifier circuits or symmetrical switching designs.
