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Do you Know BD140 PNP Transistor: Pinout, Datasheet, Features and Applications


This blog discusses the pinout, equivalent, uses characteristics, and applications of the BD140 transistor in addition to other helpful details on when and where to utilize it.




Ⅰ BD140 PNP Transistor Overview:


With its high collector-emitter and collector base voltage of 80 volts, the BD140 is a well-known PNP-type transistor that is used in many electronic circuits. It can handle current up to 1.5A or 1500mA, which enables it to be used to drive loads up to 1.5A in electronic circuits, such as high-power LEDs, relays, motors, and more. In addition to these features, the BD140 has a number of other advantages. Additionally, this transistor has a collector dissipation of about 12.5 watts, making it a strong choice for audio amplifier circuits. The transistor's minimal base voltage, also known as its saturation value, is -0.5V.


Ⅱ BD140 PNP Transistor Pinout




bd140 pinout

Figure1: bd140 pinout


 BD140 Pinout Configuration


Pin Number

Pin Name

Pin Description



Current Drains out through emitter, normally connected to ground



Current flows in through collector, normally connected to load



Controls the biasing of the transistor, used to turn the ON or OFF the transistor.


 Features and Specifications


  • Bi-Polar PNP Transistor
  • Continuous Collector current (IC) is -1.5A
  • Collector-Emitter voltage (VCE) is- 80 V
  • Collector-Base voltage (VCB) is- 80V
  • Base Current (Ib) is -0.5A
  • DC current gain (hfe) is 40 to 160
  • Available in To-225 and SOT-32 Package
  • Collector Dissipation: 12.5 W
  • Package Type: TO-126
  • Max Collector Current(IC): -1.5A
  • Max Emitter-Base Voltage (VEBO): –5V
  • Max Transition Frequency (fT): 190 MHz
  • Minimum & Maximum DC Current Gain (hFE): 25 – 250
  • Max Storage & Operating temperature Should Be: -55 to +150 Centigrade


 BD140 Equivalent Transistors


We can replaced this transistor with BD238G, MJE171, MJE702, BD792, BD170,BD180,BD231, BD790,BD792, BD792




Audio Amplifiers

Switching Loads under 1.5A

Battery Chargers

Power Supplies

Motor Driver

Darlington Pair


 Bd140 vs bd139 vs bd136 vs mje702


The transistor in the table is a list of transistors that is similar to the bd140 transistor, this comparison table will give you a wider idea about the electrical characteristics of each transistor.

At the list, we compare bd140 vs bd139, both of the transistors are the complementary pair, and then bd136 vs mje702, most of the electrical specifications of these transistors are similar to bd140.




 Bd139 (NPN)



Collector to base voltage (VCB)





Collector to emitter voltage (VCE)





Emitter to base voltage (VEB)





Collector current (IC)





Power dissipation





Junction temperature (TJ)





Transition frequency (FT)





Noise (N)





Gain (hFE)

25 to 250hFE

25to 250hFE

10 to 250hFE








  Working principle of Bd140 Transistor


  As mentioned Bd140 is a PNP transistor, so, in it the N-doped layer is embedded between two P-dopped layers. The collector and emitter are left closed when the base pin is held at the ground and are open when a signal is provided to the base pin. Since Bd140 is a PNP transistor so the majority of charge carriers are holes.

When no current is applied to the base terminal, then it will work in forward biased condition and it turns on. This condition is termed a Saturation Region.
When sufficient current is applied at the base terminal of this transistor, then it will work in Reverse biased condition and turns off. This situation is termed a cut-off region.


 Where We Can Use it


BD140 is an ideal transistor to use in educational and hobby electronics projects for example in analog circuits, Arduino projects,, and other microcontroller projects. Moreover,, it is also used in industrial electronics. The maximum load this transistor can drive is 1.5A therefore it can be used to drive a variety of loads under 1.5A. When using this transistor for a load of more than 200mA it is recommended to use a suitable heatsink with it.




 How to use BD140 Transistor


Transistors are current-controlled devices so to turn them on a little current is needed. For the BD140 Transistor, this base current is less than 10mA, as BD140 is a PNP transistor that means it will be on when the base is connected to the ground, and it will be off when a positive voltage is applied to the base of the transistor.

The simulated circuit below shows how this transistor behaves when the base of the basic circuit is connected to the ground and when it's connected to 12V of the power supply.

simulated circuit

Figure2: simulated circuit

When we turn on the transistor by connecting the base to the ground the transistor will remain on unless the voltage at the base of the transistor reaches more than the base turn-off voltage, for this transistor, it is somewhere between 0.7 -0.9V. The base of the transistor cannot be left floating otherwise there could be false triggering, which may lead to issues in the circuit. To resolve this issue, we need to add pull-up resistors as shown in the example, a 10K resistor is used to pull up the base of the transistor to VCC.


 How to Safely Long Run in a Circuit


To safely run this transistor in a circuit it is essential to not operate it above its absolute maximum ratings. Do not operate this transistor from a voltage higher than 80V DC, always use a suitable heatsink, and use a suitable base resistor to provide the required base current. Do not operate or store it in temperatures below -55 centigrade and above +150 centigrade.


 Transistor Work as a Switch


As the BD140 is a bipolar junction transistor, so it is a current-controlled device i.e.a little current is applied at the base terminal to control the transistor. The BD140 is a PNP transistor, so it will be ON when the base terminal is connected to the ground, and it will be off when a positive voltage is applied to the base terminal of the transistor. The base current of this transistor is less than 10mA.

Figure3:BD140 Transistor Work as a Switch

XIII 2D Model and Dimensions


If you are designing a PCB or Perf board with this component, then the following picture from the Datasheet will be useful to know its package type and dimensions. 


2D Model and Dimensions

Figure4:2D Model and Dimensions


XIV BD140 TO-126 Package


The package used for the BD140 transistor in the TO-126 package is a rectangular-shaped transistor package.

Plastic and epoxy are used to make this TO-126 package, most of the time transistors with moderate current and high power dissipation use this transistor package.

The TO-126 transistor package weighs less and is compact to the device circuit, at the package we can spot a hole for attaching the heat sink into it.


XV BD140 PNP Transistor Datasheet


BD140 PNP Transistor Datasheet



Frequently Asked Questions
1. What is the SMD equivalent of BD140?
2. What is the frequency of BD140?
3. What is the maximum frequency of BD140?
4. Is BD139 NPN or PNP?
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