![]() ![]() When turned ON, the current that is generated from the majority carriers, in this case the holes, starts flowing from the base-emitter part of the transistor. These terminals again should act as the terminals of a normal diode, and conduct only in one direction.Įmitter-Collector terminals: The Emitter-Collector terminals are not connected internally and hence will not conduct in either direction. To identify the device, the following points are to be kept in mind,Įmitter-Base terminal: There is a diode in between the emitter-base terminals so those two terminals should function as a normal diode and conduct in only one direction.Ĭollector-Base terminal: There is a diode similar to the collector-base terminals. ![]() Also along with the unidirectional conducting properly of diodes, we can also make use of the different resistance that the transistor offers across different terminals in a way to confirm our prediction of the device. We can use our knowledge of diodes to identify the type of transistor we are working with. As we have already discussed, the PNP transistor is a device made of two diodes connected end to end. To properly identify a device, we need to have a proper understanding of the device with which we are working with. Given that there are two types of transistors, there can be a difficulty in identifying a given transistor for proper usage. The two transistors PNP and NPN can be used interchangeably in most electronic circuits, taking into account the polarities of the voltages and the current flow’s direction. As collector voltage is always less than the base voltage and the base voltage is less than the emitter voltage, generally in a PNP transistor, the emitter voltage is always more positive than the other two terminals. The base is always negative biased with respect to the emitter. This makes the base negative and the emitter positive. Voltage across the base and emitter is according to the junction bias. The symbolic representation of the PNP transistor is the same as that of another type of transistor NPN except that now the direction of the arrow is from emitter to base whereas in NPN transistor, the arrow points from base to emitter. The above diagram shows the schematic diagram of the PNP transistor, though the thickness of each layer is not to scale. The PNP transistor configuration is shown below. The PNP transistor is a current-controlled device. From the configurations of the PN junctions as given above, we can make out that the emitter diode is always forward biased and the collector diode is reverse biased. ![]()
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