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According to me as base doping increases recombination will be less at base region so base transport factor and emitter injection efficiency will increase and as effective base width will decrease due to less doping at the base region so early voltage will decrease. am I thinking right? No options is matching.

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    \$\begingroup\$ Why does MORE base doping reduce the base recombination? \$\endgroup\$ Feb 1, 2019 at 15:26

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First of all you have a typing error in your analysis,
"According to me as base doping increases ..."
Here, it should be decreases and rest are fine;

And yes your conclusion is right ,
i.e,
$$ \text{as } \quad N_B \downarrow \quad \to \quad \gamma \text{ (Emitter Injection Efficiency) } \uparrow \quad, \quad \beta^{*} \,\, \uparrow \,\,\& \,\,|V_A| \,\,\downarrow $$

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Yes, lower base doping: Increase emitter injection efficiency (ratio of emitter:base doping)

Increase base transport factor as lower doping means less recombination for minority carriers injected from the emitter

Increase early voltage - because the base-collector junction depletion region will deplete more into the collector than the base- therefor the base edge of the depletion region will not reduce the overall base width as much.

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