When a signal is applied to the input of a transistor,it is found that the output signal is phase-shifted by $180^{\circ}$. The transistor configuration is:

If ${l_1}, {l_2}, {l_3}$ are the lengths of the emitter,base,and collector of a transistor,respectively,then:

Given below are two statements:
Statement $I:$ In a typical transistor,all three regions emitter,base and collector have same doping level.
Statement $II:$ In a transistor,collector is the thickest and base is the thinnest segment.
In the light of the above statements,choose the most appropriate answer from the options given below.

In an $npn$ transistor,$10^{10}$ electrons enter the emitter in $10^{-8}$ second. If $1\%$ of electrons are lost in the base,the fraction of current that enters the collector and the current amplification factor are respectively:

In the $CB$ mode of a transistor, when the collector voltage changes by $0.5 \ V$, the collector current changes by $0.05 \ mA$. What is the output resistance in $k\Omega$?

$A$ common emitter transistor amplifier has a current gain of $50$. If the load resistance is $4 \ k\Omega$ and input resistance is $500 \ \Omega$, the voltage gain of the amplifier is