Kicking ass, engineering style. A product design firm in San Francisco, we specialize in building cool smartphone accessories. Join us for coffee sometime!
Hello friends, we are going to discuss about the parts 2 for the mixed phenomena that will happen inside the bipolar junction transistor. For that we have taken a PNP transistor in the figure, you can see the PNP transistor and in this figure we can see that we have applied FEB potential here, junction is out in the reverse pass, the JE junction is in the forward pass, the division layer width in the JC junction will be cut with respect to the JE junction division layer width. Now we have the potential that is VBC with making the JC junction reverse pass. So this VBC in a collector junction reverse pass to the depletion width at the JC junction will because with respect to the depletion width at the Junction. On this case and see that if we increase the base to collector voltage then the depletion layer width at the JC will decrease and if the depletion layer width at JC increases so the effective base width decreases. If the effective base width decreases then we can say that the base width is dependent on the base to collector voltage which was known as the base width modulation that we have seen in the earlier lectures which was also called the early effect. Now in this way if we increase the base to collector voltage rigorously then at some value of VBC what will happen? The depletion layer width with position here will be such that the whole VBC's region will be covered by the depletion region of JC and at this moment the effective base width will be in. So if the total base that is if this total base region is now covered with the depletion region then the holes which are moving from this emitter region to the collector region to the base and the holes can directly move from this emitter to the collector region without any recombination in the base region because now there is no existence of the base region. So the hole in the base region is covered by the VBC. That's why this phenomena when the effective base width is 0 for particular voltage of VBC this is called the punch through or the bridge through. And in this punch through and bridge through there are some consequence that will happen due to this punch through or bridge through or we can say that this punch through and bridge through phenomena is a special case of the base width modulation when the base width will be completely 0 and the goal of the depletion region will cover the total base region. Let us see the consequence of the effect of this base width modulation that is the first consequence that will happen due to this base width modulation that when VBC will increase then the effective base region will cause the depletion region and the JC junction will cover almost all the area of the base. That's why there will be less recombination happens inside the base region. That's why the alpha value will increase by a significant amount due to this distance. Second one with the decrease of the base region or the width of the base region the concentration gradient that we can write that is the concentration gradient of the minority barrier of minorities areas is increased within the base. That's why we can say that the IE will be nearly equals to IPE where IPE is the current in the electron due to the holes. So we can say that in this case the IE current will be nearly equals to the IPE. So in the third case we can say that for large value of VCP the width of the base region will be nearly equals to zero. This is called the punch to or the consequence that can happen due to the base width modulation and the punch to is one of the consequence of the base width modulation. So this is all about the punch to or the risk of phenomenon that we can write the 5 hertz also. Thank you.
