# Why Emitter current increases with increase in collector to base voltage in common base configuration of a BJT?

It is said from early effect that with increase in collector to base voltage there is decrease in base width due to which $\alpha$ (the current gain) increases due to lesser recombination of holes and electron, so with increase in $\alpha$ emitter current should decrease according to equation

$$I_E=\frac{I_C}{\alpha} \, .$$

Also, concentration gradient of minority charge carriers in base region increases and due to which more majority charge carriers (of emitter region) come from emitter to base region and hence increasing emitter current.

Both of these effects are in contradiction to each other, so does it happen like latter effect is more than the former?

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• Please include a circuit diagram with all circuit questions. – DanielSank Dec 26 '16 at 19:18
• Your present a false dichotomy. Base-width modulation due to $V_{BC}$ (aka Early Effect) is a latter modification to the Ebers-Moll model, but prior to the development of the Gummel-Poon model in 1970, which then included variation due to $V_{BE}$ (aka Late Effect.) Gummel-Poon (and its modifications, as well as the VBIC model and still more versions since) includes a more complete treatment of the physics. I'd recommend (relatively inexpensive) books such as Millman's 1979 edition of "Microelectronics" for a detailed walk-through. – jonk Dec 27 '16 at 5:59
• Both descriptions state a larger collector potential yields a larger collector current – sstobbe Oct 1 '18 at 2:33
• Possible duplicate of BJT gain.Width of base region vs collector current – try-catch-finally Dec 21 '18 at 6:11