The ratio of I CE to I BE is called the CURRENT GAIN of the transistor and is given the symbol Beta, β.Ī set of static characteristic curves (graphs) can be drawn to show the operating parameters of a bipolar transistor for different DC currents and voltages. The ratio of the collector-emitter current to the base-emitter current is generally constant, provided that the collector-emitter voltage V CE remains constant.

The bipolar transistor has three regions known as Emitter, Base and Collector and is a current operated device where a small base current can control a much larger collector-emitter current. The direction of arrow heads at the emitter in an NPN and PNP transistor are opposite to each other. The symbol used for a transistor has an arrow head in the emitter pointing from the P-region towards the N-region to indicate the direction of a conventional current flow. The PNP transistor is a complement of the NPN transistor. This results in what is known as an NPN transistor or a PNP transistor. For a transistor to operate as either an amplifier or an electronic switch, it requires external voltages to be applied between all of its junctions.Ī transistor consists of two PN junction which are formed by joining together either a p-type or n-type semiconductor layers between a pair of opposite types.

The Bipolar Junction Transistor is a three-layer solid-state semiconductor devices which controls the flow of electric current through itself by the application of a different voltage levels onto its terminals.

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