![]() ![]() ![]() The direction of the arrow sign for a PNP transistor is from the emitter towards the base (i.e. collector has no arrow sign) The direction of the arrow sign reflects the direction of flow of conventional current. The arrow sign in PNP and NPN transistors symbols is also located on the emitter (i.e. On the contrary, an NPN transistor consists of two N-type semiconductor materials separated through a narrow P-type semiconductor, or an NPN transistor is formed by sandwiching a P-type material between two N-type materials. In other words, the PNP transistor comprises an N-type material, which is sandwiched between two P-type materials. As can be seen from the figure, a PNP transistor consists of two P-type semiconductors, which are isolated through a narrow N-type semiconductor. In diagram 4.3 construction and symbol of the junction transistor have been illustrated. One type is called PNP while the other one is NPN transistor. The two junctions which are produced between these three layers are called emitter-base (E/B) junction and collector- base Junction (C/B) (figure 4.2)īipolar junction transistors are available in two types. Terminals alongside Emitter, Base, and Collector have been shown as C, B, and E in the diagram. As a transistor has three layers, therefore, three terminals are fitted with these three layers. Both the junctions form three regions which are called emitter, base, and collector. The junction is manufactured through sandwiching layers of P and N-type semiconductors with a pair of opponent types. Are comparatively cheaper than vacuum tubesĪs characteristics of a transistor change with variations in temperatures, therefore reasonable outcomes are not possible at higher temperatures, which is one of its greatest drawbacks.Ī junction transistor basically comprises two PN junctions which are shaped in the form of a single semiconductor crystal.Strong from the construction point of view, therefore can withstand jolts and trembling situations.Due to the small space requirement, instruments composed of it are usually small. They are lighter in weight and physically small.They start working immediately, which results in the conservation of electrical energy. Nor do they require any power for this purpose. Thus, electronic instruments do not develop defects for a long time. Transistors have the following advantages compared to a vacuum tube If two PN junctions’ diodes are interconnected in mutually reverse directions, a transistor is formed. holes and electrons), therefore, it is called a bipolar device. Further, as the working of the transistor depends on the flow of majority and minority carriers (i.e. The name transistor has been derived from “Transfer Resistor” which means that it can transfer its internal resistance to the emitter, low resistance of the base circuit to the collector, to very high resistance of the base circuit. All three were awarded a noble prize for this remarkable invention. This device was invented by William Shockley, John Barden, and Walter H. Both these junctions form three regions, which are called emitter, base, and collector. Bipolar Junction Transistor IntroductionĪ bipolar junction transistor is a device consisting of two back-to-back PN junctions.
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