The emitter is the portion on one side of the transistor which emits electrons or holes to the other two portions. These terminals are briefly discussed here. These terminals are knowns as collector, emitter and base. The junction of the base with emitter is known as the Emitter-Base junction while the junction of the base with the collector is known as the Collector-Base junction. The middle portion (base) forms two junctions with the emitter & collector. The emitter and collector sandwich the base in between them. These three portions are called Emitter, Collector, and Base. These transistors are known as PNP or NPN bipolar junction transistors depending on whether P or N-type is sandwiched.īasically, transistors have three portions and two junctions. BJT transistors are formed after connecting two PN junctions back to back. When P-type and N-type material are connected together then it becomes a PN-junction diode. While in P-type semiconductor, the number of holes is greater than the number of electrons. If the number of electrons are greater than the number of holes (positive carriers) then that is known as N-type semiconductor material. BJT is a three-terminal device having two junctions.Īfter doping an intrinsic semiconductor with Trivalent or Pentavalent impurities a P-type semiconductor or N-type semiconductor respectively is made. Two PN junctions’ diodes are sandwiched together to form a three-terminal device knows as BJT transistor. These extrinsic semiconductors are PN junction diodes. In other words, BJT is formed by the “sandwich” of back to back extrinsic semiconductor materials. Constructionīipolar junction transistor is formed by the combination of two back-to-back doped semiconductor materials. This main current is controlled by a very small current at the base terminal. The current flows from emitter to collector or from collector to emitter depending on the type of connection. field effect transistor uses only one type of charge carrier. What is BJT – Bipolar Junction Transistor?īipolar junction transistor (BJT) is a bidirectional device that uses both electrons and holes as charge carriers. In short, a transistor has high resistance in the input section while low resistance in the output section. In other words, a transistor transfers the resistance from one end to the other. Good to Know: The name of Transistor is derived from the combination of tow words i.e. Nowadays, the use of BJT is decreasing because CMOS technology took place in the design of digital ICs. The invention of transistor changed the concept of electrical circuits to integrated circuits (IC). While the first transistor was invented 70 years ago but till now it changed the world from mysterious big computers to small smartphones. Voltage Divider Bias or Potential Dividerīipolar junction transistor (BJT) was invented by William Shockley and John Bardeen.Advantages of Fixed Bias with Emitter Configuration.What is BJT – Bipolar Junction Transistor?.
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