The direction of the arrow indicates the direction of current in the transistor.
The direction of flow of current is same as the direction of flow of holes, this is because the holes are positive charge carriers and current is also because of the positive charge carriers. As a consequence, current will flow from emitter to collector. The remaining holes will travel move towards collector region. Due to the lightly doped base region, only a few holes will recombine with electrons.
The holes present in emitter region will move towards the base region to recombine with electrons. The emitter terminal of PNP transistor is connected to positive terminal of the battery while the base terminal of PNP transistor is connected to the negative terminal of the battery. The PNP transistor will conduct only when the base-emitter junction is forward biased and collector based junction is reversed biased. The holes are responsible for conduction in PNP transistor.
The majority charge carriers in PNP transistor are holes. PNP Transistor is an acronym of Positive-Negative-Positive, it is formed by sandwiching an N-type layer of the semiconductor between two layers of P-type semiconductor. The base is smallest in comparison to other regions. The size of the collector is greatest among all regions. This is because the direction of flow of current is opposite to that of flow of electron. The direction of electrons is from the emitter to collector thus, the direction of current will be from collector to emitter. Thus, the emitter is the highly doped region of the transistor. If we will arrange the base, emitter and collector in increasing order of their doping intensity, the base will hold the first position followed by collector and last in the list will be the emitter. Therefore, only a few electrons will recombine with holes and the remaining will flow towards collector region. The base is lightly doped region thus consists of fewer holes. The electrons which are present in the emitter junction will repel from the negative terminal of the battery and move towards the base. In this emitter junction is connected to the negative terminal of the battery while the base of the transistor is connected to the positive terminal of the battery. The NPN transistor starts conducting when the Emitter-Base junction is forward biased.
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The full form of NPN transistor is Negative-Positive-Negative. The majority charge carriers in NPN transistor are electrons. NPN transistor is formed by sandwiching P-layer of the semiconductor between two layers of N-type semiconductor. PNP transistor is less used in comparison to NPN transistor. NPN transistor is used in most of the applications. Holes are less mobile in copmparison to electron thus, PNP transistor provides less condcution. It acts like current sink as it completely sink the current towards base terminal.Įlectrons possess high mobiltiy thus conduction is more It acts as current source as it sources current from base terminal of transistor. Transistor which consists of one layer of N-type material sandwiched between two layers of P-type semiconductor.Įlectrons flow from emitter to collector. Transistor which consists of one layer of P-type material sandwiched between two layers of N-type semiconductor. The other significant differences are described with the help of comparison chart.Ĭontent: NPN Transistor Vs PNP Transistor
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