![]() More than 95℅ emitted electrons enter into the collector and only 5℅ recombine with the holes in the base, therefore, the collector current I C is much larger than the base current I B. The resistance is transformed from one side to another side therefore, it is called a transistor. Resistance is decreased in the emitter-base side and becomes conductor, whereas resistance is increased in the collector-base side due to this the current majority stops in the collector-base side but the reverse current continues to flow. The current flow is more in the emitter-base side current decreases in the collector- base side. Below is the circuit diagram of common emitter configuration.Īfter the circuit is connected the depletion layer of the emitter-base is decreased whereas the depletion region of the collector- base is increased. ![]() Similarly, we can have a common emitter configuration and a common collector configuration.īut mostly we use a common emitter configuration because the most popular use of transistor is to make the amplifier and the best amplification is done by a common emitter configuration. In the above circuit diagram, the base terminal is common for the emitter and the collector so, therefore, it is called a common base configuration. And in the base and collector circuit, it is always reverse biased. There is a rule for the emitter and the base that is the battery connected should always be in forward biased. So, we usually prefer NPN transistors for better results.Įach NPN junction has two terminals we connect a cell between them do there is a potential difference across it. The mobility of electrons is better than the mobility of holes, therefore, NPN transistor works faster as compared to PNP transistors. In NPN transistors the majority charge carriers are electrons and in PNP transistors the majority charge carriers are holes. Usually, NPN transistors are used because it is easy to design them. The current flows in the direction from the collector to the emitter. The NPN transistor turns on when the current flow through the base of the transistor. If the arrow is pointing outside then it is NPN transistor and if it is pointing inwards then it is PNP transistor.Ī transistor, in which there is one p-type semiconductor that is doped by two n-type semiconductors from both sides are called NPN transistors. To identify whether it is NPN or PNP we use this arrow. The arrow shows the direction of the electric current and the electric current always flows from positive to negative. Here, which has an arrow is known as emitter, the base is always in the center. The base size is small and it is lightly doped, the emitter size is moderate (between the base size and the collector size) and the doping is strong, collector size is large as compared to base and emitter and the doping is moderate (between the base and emitter doping). Here the collector and the emitter old of p-type and the base are of n-type. In PNP transistors instead of electrons, the emitter emits holes and they are collected by the collector. The PNP transistor turns on when there is no current at the base of the transistor. In PNP transistor they are two differences between both P, that is doping and the size of both p is different.Ī transistor in which there is one n-type semiconductor that is doped by two p-type semiconductors from both sides is called PNP transistor. Thee are two types of transistors NPN and PNP transistor. The emitter emits the charges and these charges are collected by the collector. The transistor has three regions that are emitter, base, collector. In a transistor, one semiconductor is sandwiched from both sides by another semiconductor. With the help of diodes, amplification of the signal is not possible and that is the reason we use transistors. Semiconductors are basically used in manufacturing two devices that are diodes and transistors.
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