bd140 transistor

In this article we are going to explain the BD140 power transistor, it is a very common transistor nowadays. It is a PNP BJT transistor and they had general-purpose applications.

The BD140 transistor’s power handling capabilities will help them to stay in first place at the general application on modern digital circuits.

In this post, we include main points at BD140 datasheet, BD140 working process, BD140 projects, and also different aspects of BD140 transistor type that include technical and physical specifications.

BD140 datasheet

BD140 Pinout

BD140 Pinout
BD140 Pinout
  1. Emitter (e) – pin01
  2. Collector (c) – Pin02
  3. Base (b) – Pin03

The pinout details of the BD140 transistor is pin01 emitter starts from left to right, then pin02 collector and last base pin03.

And at the emitter pin, the PNP indication is marked, that is the current flow towards the transistor.

BD140 package (TO-126)

This type of package is used at BD140 transistor, general power transistor had this kind of package. The hole at the BD140 transistor body helps them to attach with the heatsink.

The to-126 package is made with epoxy and plastic material, this makes them less expensive and has more applications.

BD140 voltage ratings

  • Collector – base voltage = 80v
  • Collector – emitter voltage = 80v
  • Emitter – base voltage = 5v

The base-to-emitter voltage of BD140 is 5v, this is the biasing voltage need for the bd140, and due to this range, and the BD140 had applications at microcontroller circuits.

The collector-to-emitter voltage of BD140 is 80v, which is the maximum voltage taken output.

The collector-base is the input to output voltage taken the output from BD140 transistor.

BD140 current ratings

  • Collector current = 1A
  • DC current gain = 40 to 250 Hfe

The collector current is the maximum current provided from the device or the maximum capacity of current at BD140.

The DC gain of the BD140 transistor is at the range of 40 to 250 Hfe, this value will determine the amplification capacity of the component.

It can handle 1amp current, due to which we can drive high-power LEDs, relays, and motors.

BD140 temperature capacity

  • Maximum operating junction temperature = 150˚C
  • Thermal resistance = 10˚C/W
  • Collector power dissipation = 12w

The collector dissipation of the BC140 transistor is 12w, this will make the audio amplifier circuit more capable.

BD140 transition frequency

The transition frequency of the BD140 transistor is 50MHz, this particular frequency value supports them to work with microcontroller applications.


The SMD version of the BD140 transistor is a BCP53 surface mount transistor, the BCP53 SMD transistor had a SOT-223 package.

BCP53 pinout
BCP53 pinout

The BCP53 pinout will be like Pin01 is base, Pin02 and Pin04 is collector, and Pin03 is the emitter.

It is a medium voltage load switching transistor, they had applications on output stage audio amplification circuits.

BD140 Equivalent

The BD140 transistor had multiple equivalent transistors such as BD140G, BD170, and MJE252.

BD140 complementary

The BD140 had a main complementary NPN transistor which is BD139, using both these complementary transistor types we had different applications.


BD140 transistor projects

  1. BD140 – BD139 H-bridge circuit

BD140 – BD139 H-bridge circuit
BD140 – BD139 H-bridge circuit


The H-bridge is the main application of BD140 transistor combined with complementary NPN transistor BD139, the H-bridge circuit is used to drive motor.

When we need to run a DC motor, we need a high amount of power and enough power is delivered to run two DC motor smoothly.

We can also control the direction of rotation of the motor at the projects, these types of applications are used at microcontroller circuits.


  1. BD140 transistor as a switch

BD140 transistor as a switch
BD140 transistor as a switch

The transistor works as the switch is the common project among general purpose applications, but the BD140 is called a power transistor.

When a voltage is applied to the base of the transistor, the transistor becomes ON and the transistor remains at ON state till the next pulse strikes the base terminal again.


  1. BD140 transistor as an amplifier

BD140 transistor as an amplifier
BD140 transistor as an amplifier


The circuit above is the mono amplifier circuit using BD140 PNP transistor, along with BD140, transistors like tip2955 and A1015 are used with the circuit.

The working process is simple and easy because the A1015 and BD140 PNP transistors made an initial amplification and then TIP2955 combine both the signal to high power output towards the two speaker load.

Advantage of BD140 transistor

  • It is very easy to turn ON and turn OFF this transistor
  • It can the ability to carry higher current at ON state
  • They block high voltages in ON state
  • They operated at switching frequency in the range of 10 to 15khz
  • The ON-state voltage drop across this transistor is low


Disadvantages of BD140 transistor

  • They cannot operate safely above the switching frequency of 15khz
  • They may be damaged due to thermal runaway
  • Reverse blocking capacity is very low


BD140 transistor application

  • Audio amplifier
  • Battery charger circuits
  • Power supplies
  • Motor driver circuit
  • Inverter
  • SMPS

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  1. Bonjour
    Sur le symbole du BD140, vous avez inversé l’émetteur avec le collecteur !!!
    Jacques Baranski.

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