I know that due to early effect in a npn transistor the effective base width reduces.However I can't understand how this will lead to an increase in emitter current. Some sources say that the charge concentration gradient increases due to this early effect and hence the increase in emitter current but how can the charge gradient increase since that is determined by doping. Other sources claim that this early effect will reduce the base current leading to increase in collector current which therefore means that the emitter current increases, this i think is wrong as everyone here knows. Can any one please explain it then. Any help will be appreciated Thank you.

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    \$\begingroup\$ How are your search skills ? electronics.stackexchange.com/… \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 16 at 13:41
  • \$\begingroup\$ Thank you. I am new here. I'll look up the link \$\endgroup\$ – Yasir Sadiq May 16 at 13:42
  • \$\begingroup\$ There were 200 results, not sure why you think 201 explanations will help electronics.stackexchange.com/questions/231474/… \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 16 at 13:47
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    \$\begingroup\$ @YasirSadiq I was hinting at you to search harder, I just responded quick to show it wasn't hard and besides I saw LvW's answer and he has similar deep experience as myself but better on this question. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 16 at 16:55
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    \$\begingroup\$ @Yasir Sadiq... I also agree that the figure you have shown comes from a well-known book (Boylestad and Co.). Hower, I suppose the shown dependence of IE on VCB is unrealistic (enlarged) - in comparison to the influence on IC. In this context, the authors state somewhat later (see figure 3.10a): "In fact, increasing levels of VCB have such a small effect on the characteristics that as a first approximation the change due to changes in VCB can be ignored".... \$\endgroup\$ – LvW May 17 at 11:52

following up on comment of "LvW", the mechanism would predict the highest_Beta transistors will have the least Early Effect (have the flattest I_out).

And because there is a small region of bulk silicon between the base contact for metal and the actual base region that is sandwiched between emitter and collector, with the Ibase * R_bulk_base == voltage varying as Ibase varies, it sees the LOWER NOISE transistors (which have lower R_bulk_base) will have lower Early Effect.

I realize the parameters we use are Abstractions, are parts of modeling.

SUMMARY: I'm thinking high_beta low_noise transistors will be the best current sources.

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  • \$\begingroup\$ I fail to understand how this is related to my question. \$\endgroup\$ – Yasir Sadiq May 17 at 8:29

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