![]() So, positive holes are the majority carriers in this region. Hence, Current through the collector junction flows from Collector region to Base region.Ĭonstruction and Symbol of PNP Transistor Emitter region (E)Įmitter has medium size and greater doping level. So, electrons flow from Base to Collector region. The electrons coming from Emitter enters in Collector region from Base region. In NPN Transistor, collector region has n-type of doping. This region has greater size and medium doping concentration. Collector region (C)Ĭollector of a Transistor collects the charges coming from Emitter via Base. Doping concentration of Base region is made very small to reduce the recombination of holes with the electrons coming from Emitter region. In NPN Transistor the doping type of Base is p-type. Base region (B)īase region has smaller size and smaller doping concentration. The current at Emitter terminal is the Emitter current ( I E). Therefore, in symbol of NPN transistor we can see that the direction of current flow is outward from the Emitter terminal. So, the direction of current flow through Emitter junction is along Base region to Emitter region. Since Emitter emits charges to Base region, the free electrons flow from Emitter to Base of the NPN Transistor. So, free electrons are the majority carriers in this region. This region has n-type doping materials like Arsenic, Phosphorus etc. Construction of NPN BJT TransistorĬonstruction and Symbol of NPN Transistor Emitter region (E)Įmitter has medium size and greater doping level. Conventional current flow will be in the direction of the flow of Holes and in the opposite direction of electron flow.Ĭonstruction of NPN and PNP Transistor are almost the same, but there are some difference in doping types, direction of current flow, symbols etc.Ĭlick here to check the difference between NPN and PNP Transistor. Emitter emits the charges towards Base region and finally charges are collected in Collector region after passing through the Base region.Base has smallest doping concentration to reduce electron-hole recombination. Doping of Emitter region is greater than that of Collector and Base region.Collector has greater size to reduce heating effect, Emitter has medium size and Base has lower size.The junction between Emitter and Base is the Emitter-Base junction or simply Emitter Junction and the junction between Collector and Base is the Collector-Base junction or simply Collector junction. Thus, these three region forms two p-n junctions. These three regions are alternatively doped with different types of doping (n-type or p-type). All the Transistors have three regions – Emitter, Base and Collector.The size, doping type, doping concentration and direction of current flow in the three layers are the key terms to describe the construction of the Transistor. These regions are Emitter, Base and Collector. We already know that BJT consists of three doping regions on the semiconductor substrate. ![]() Construction of Bipolar Junction Transistor (BJT) Thus, holes are the majority carriers in PNP Transistor. Emitter, Base and Collector have the doping type as p-type, n-type and p-type respectively. Here also the negative and positive terms indicate the the doping type of the three parts or layers of transistor. PNP Transistor has its full name as Positive Negative and Positive Transistor. One can form a PNP Transistor by inserting a n-type region between two p-type region in a semiconductor substrate. Thus, free electrons are the majority carriers in NPN Transistor. Doping type of Emitter and Collector are n-type and doping type of Base is p-type. This negative and positive terms refer the doping type of the three regions of the Transistor. The full form of NPN Transistor is Negative Positive and Negative Transistor. When a p-type region is sandwiched between two n-type region in a semiconductor substrate, a NPN transistor forms.
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