What is BJT, Definitions, Advantages & Disadvantages

Authored By: Ankita Prajapati

BJT stands for Bipolar Junction Transistor. It is an electronic component that controls current flow between two terminals by using a small current applied to a third terminal. It is a semiconductor device, which is made of two layers of a semiconductor material, such as silicon, with different doping concentrations. 

These two layers are called the emitter and collector, and the third terminal is called the base.

When the base current is applied, the emitterbase junction is forward-biased, and the collectorbase junction is reverse-biased.

This allows the current to flow from the emitter to the collector. The amount of current flowing from the collector to the emitter is controlled by the base current.

This current flow is known as amplification because the small base current is amplified to control a much larger collector current. BJTs can be used in a variety of applications, such as amplifiers, switches, oscillators, and other digital circuits. They are also commonly used as transistors in power supplies.

BJTs are more efficient than other types of transistors, they are more reliable and can handle higher power levels. BJTs are widely used in consumer electronics, such as computers, televisions, radios, and other electronic devices.

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  1. Low cost
  2. High switching speed
  3. High input impedance
  4. Wide range of current gain 
  5. Good linearity and low distortion 
  6. Low noise.ts
  7. Easy to interface with other componen


  1. High power consumption
  2. Limited current and voltage handling capabilities 
  3. Poor frequency response 
  4. Prone to thermal and secondary breakdowns 
  5. Susceptible to latchup problems

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They are also used in industrial and medical applications, such as power supplies, medical imaging, and medical diagnostics.

BJTs have evolved over time, and they continue to be improved to meet the demands of modern electronics. They are reliable, efficient, and costeffective, and they continue to play an important role in todays electronic devices.

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