In a transistor,the base is very lightly doped as compared to the emitter because by doing so:

$A$ working transistor with its three legs marked $P, Q$ and $R$ is tested using a multimeter. No conduction is found between $P$ and $Q$. By connecting the common (negative) terminal of the multimeter to $R$ and the other (positive) terminal to $P$ or $Q$,some resistance is seen on the multimeter. Which of the following is true for the transistor?

If the value of $R_e$ is zero then voltage gain is $200$. Find the voltage gain when $R_e$ is $2 \, k\Omega$.

For a constant collector-emitter voltage of $8\,V$,the collector current of a transistor changed from $4\,mA$ to $6\,mA$,whereas the base current changed from $20\,\mu A$ to $25\,\mu A$. If the transistor is in the active state,the small signal current gain (current amplification factor) will be:

$A$ transistor is connected in a common base circuit with $\beta = 75$. For an emitter current of $5 \text{ mA}$,the value of the collector current is ........ $\text{mA}$.

In a transistor,the base is made very thin and is lightly doped with an impurity because: