BD681 Transistor Pinout, Equivalent, Features, Applications, Where and How to Use It

Today we are going to discuss BD681 transistor pinout, equivalent, features, applications, where and how to use it and other useful information about this TO-126 package darlington transistor.


BD681 Transistor Pinout, Equivalent, Features, Applications, Where and How to Use It



Absolute Maximum Ratings:

  • Package Type: TO-126
  • Transistor Type: NPN Darlington
  • Max Collector Current(IC): 4A
  • Max Collector-Emitter Voltage (VCEO): 100V
  • Max Collector-Base Voltage (VCBO): 100V
  • Max Emitter-Base Voltage (VEBO): 5V
  • Max Collector Power Dissipation (Pc): 40 Watt
  • Minimum DC Current Gain (hFE): 750
  • Max Storage & Operating temperature: -65 to +150 Centigrade


PNP Complementary:

PNP Complementary of BD681 is BD682


Replacement and Equivalent:

BD683, BD337, NTE2345, BD335, 2SD1831, MJE803, MJE802, MJE801, MJE800.


BD681 Transistor Explained / Description:

BD681 is a medium power transistor available in TO-126 package. The transistor is designed to be used in switching and medium power linear applications or amplifier applications. BD681 is a transistor of BD6XX series which also contains other transistors such as BD675, BD675A, BD677, BD677A, BD679 and BD679A. The PNP complimentary series of these transistors are BD676, BD676A, BD678, BD678A, BD680, BD680A.

Coming back to the BD681 transistor the maximum collector-base voltage is 100V, max collector-emitter voltage is also 100V, max emitter-base voltage is 5V, max base current is 100mA, max collector current is 4A and max collector dissipation is 40W.

As mentioned above the transistor is designed to use in applications such as switching and amplification. So you can use it in a wide variety of applications such as driving different types of loads under 4A and amplifying different types of signals.


Where We Can Use it & How to Use:

The transistor can be used in wide variety of applications such as controlling motors, driving loads, and amplifying different types of electronic signals. A more detailed list of its applications is mentioned under the Applications heading below.

For using the transistor first check its pinout and then connect the base pin with the signal which you want to amplify on drive on load. If you are using it as a switch then connect its emitter pin with the positive supply of the circuit and its collector pin with the positive lead of the load and the negative load of the lead will be connected with the negative supply of the circuit. But if you are using it as an amplifier then the collector output will be used as an amplified signal. Moreover, you also have to use some passive components in the circuit to build a better quality amplifier circuit.



Motor Control

LED Drivers

Pulse Generator

Audio Amplifiers

Voltage Regulation

Switching Circuits

Battery Operated Applications

DC to DC Converters

Power Supplies

Voltage inverters


Safe Operating Guidelines:

Below are some safe operating guidelines for this transistor.

  • For getting good and long life performance with this transistor it is important to not use it to its absolute maximum ratings and always stay 20% below from these ratings.
  • So as you see the max collector-emitter voltage is 100V so do not drive load of more than 80V.
  • The maximum collector is 4A therefore do not drive load of more than 3.2A.
  • Always use the transistor in surrounding temperature of between -65°C and 150°C.



To download the datasheet just copy and paste the below link in your browser.

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