Question

Match the following:
List-I
A. The current gain of a BJT will be increased
B. The current gain of a BJT will be reduced
C. The break-down voltage of a BJT will be reduced
List-II
1. The collector doping concentration is increased
2. The base width is reduced
3. The emitter doping concentration to base doping concentration ratio is reduced
4. The base doping concentration is increased keeping the ratio of the emitter doping concentration to base doping concentration constant
5. The collector doping concentration is reduced

Answer 1

Ans : (a)

As the base width of the BJT is reduced then the recombination current (base current $I_B)$ decreases as a resuly colletor current $\left(I_C\right)$ increases. So, the current gain of the BJT increases.
$\alpha =\frac{I_C}{I_E}$
* If the emitter doping concentration to base doping concentration ratio is reduced then the emitter injection efficiency decreases, so the current gain $\left(\alpha \right)$ of BJT reduces.
* If the collector doping concentration is increased then the breakdown $\left(V_{BR}\right)$ of a BJT will be reduced.