When the circuit is turned on, higher potential at the base region of the NPN transistor pulls the electrons from the emitter of NPN transistor towards it. That is, for a NPN transistor, Base is more positive with respect to Emitter and Collector is more positive with respect to Base. Here, Emitter-Base junction is forward biased and Collector-Base junction is reverse biased. The figure shows the most common configuration of NPN transistor. Working of BJT Transistor - NPN Transistor Therefore, a BJT transistor can be used as an amplifier. The controlled power can be higher than that of the input controlling power. Similarly, majority carrier flow from emitter to collector can be controlled by base current. Quantity of water flowing through the pipe can be controlled by moving the knob of the tap. Working of a BJT transistor is analogous to a water tap. Working of BJT Transistorīipolar Junction Transistor can be defined as a three terminal current controlled device. All other properties of NPN transistor and PNP transistor are same. Mobility of electrons is higher than that of holes and therefore, NPN transistor are more preferred in electronic circuits. In NPN transistor, electrons are the majority carriers and in PNP transistor, holes are the majority carriers. Structure and circuit symbol of PNP transistor and NPN transistor are shown in the above figures. Structure and Symbol of Bipolar Junction Transistor - NPN Transistor, PNP Transistor In one method, N layer is sandwiched between two P layers called PNP transistor and in the other one, the P layer is sandwiched between two N layers called NPN transistor. Majority carriers from emitter are finally collected at the collector region of the BJT transistor.Ī BJT transistor can be constructed in two ways. Majority carriers from the emitter pass through the base region and its flow can be externally controlled.
Base region is a thin, lightly doped region and is sandwiched between emitter and collector. Emitter is a heavily doped region of the BJT transistor which provides majority carriers into the base region. Three layers Emitter, Base and Collector of a BJT transistor are formed by sandwiching alternative P and N layers. Bipolar Junction Transistor is a three layer semiconductor device, which has a wide range of application in the semiconductor industries.
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