A low-powered signal becomes a higher-powered signal when the input current caused by a low voltage appears almost undiminished in the collector circuit, but at a higher voltage. It takes only a small amount of power to cause current in the transistor's forward-biased base-emitter input circuit yet almost all this easily forced input current appears in the collector circuit. Since the base region is made very thin, most of the majority carriers that flow from the emitter will be caught by the strong electric field in the collector base junction before they can exit through the base connection. It is therefore very easy to cause current in the transistor's input circuit. The base-emitter diode in the transistor offers a very low resistance to current flow when it is forward biased. When the base-emitter junction is forward biased, the carriers needed for current in the collector circuit find their way into the collector. Its job is to emit or inject electrons into the base. The very small current in the collector circuit under these conditions is because the p-type material in the base is starved for the n-type majority carriers that the collector circuit requires if it is to conduct a significant current. Which is highly doped in transistor In most transistors, emitter is heavily doped. The collector-base diode is reverse biased so that almost no current will flow unless the base-emitter diode is forward biased. The collector-base diode and the base-emitter diode appear to be in series, connected back-to-back.
It has to emit charges into the collector through the base. Emitter - The emitter is the highly doped terminal of the transistor. An n-p-n transistor configured as a common-emitter amplifier, where both the base and the collector circuits are referenced to the emitter, is normally connected with a positive voltage on the collector, as referenced to the emitter. These differences give each of the terminals it’s uniqueness. These variations, called common base, common emitter, and common collector, produce different circuit actions each with unique characteristics. Thanks for giving us your valuable time.There are three ways to connect a bipolar junction transistor into a working circuit, depending upon which of the three transistor elements is chosen as the common reference for the other two elements.
#TRANSISTOR BASE EMITTER COLLECTOR FREE#
If you have any query and suggestion related to this article feel free to comment below. Thus, the base region is thin and lightly doped region. For good amplification process, we required less base current and more collector current So we try to reduce base current by less doping of base region. Hope you understand clearly why the base is lightly doped in bjt or in the transistor. Collector region of a transistor is highly doped so collector region has more width than other two. The base region is lightly doped so that width of the base is less. The width of the region depends upon their doping. That’s why in all the methods we always reduce the base current like less doping of the base region, the high resistance value of base resister and high beta value.Īs per above, we saw base is lightly doped. If the doping in the base region will br high than recombination rate also will be high in the base region, if recombination rate is high than base current will also be more, But for amplification, we need base current as small as possible. Also, we know only 5 % of emitter current transfer to base and 95 % current passing to the collector.īase region doping of the transistor is one of the major factors in deciding the amplification. Thus, more current passing to the collector side or an output side. Because of this reason base is lightly doped. So output current ( collector current ) is reduced. So if we highly doped base region so more current passing to base terminal. So for collector current ( Ic ) = Ie – IbĬonductivity is increase with an increase in doping. As per transistor operation, we know emitter current is the total of collector current and base current. So we have a question why base of the is thin and lightly doped? Why the base of transistor is thin and lightly doped?Īnswer: Think transistor as a switch, between emitter and collector, base as a switch key. In PNP and NPN transistor, collector region has more width than other two regions and base region is thin region.
We saw all the terminals of both types of transistor. In previous, we saw the construction of PNP and NPN transistor construction. In the transistor, there is the difference in the width of the region. In an NPN transistor or PNP transistor, there are three regions of the transistor. Either two P-type and one N-type or two N-type and one p-type. In previous articles, we saw there are three semiconductors in the transistor.
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