$NPN$ transistors are preferred to $PNP$ transistors because they have

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:

In a common emitter amplifier,a change of $0.2 \text{ mA}$ in the base current causes a change of $5 \text{ mA}$ in the collector current. If the input resistance is $2 \text{ k}\Omega$ and the voltage gain is $75$,what is the load resistance used in the circuit?

In the following common emitter circuit, if $\beta=100$, $V_{CE}=7 \, V$, $V_{BE}$ is negligible, and $R_C=2 \, k\Omega$, then $I_B=$ (in $\, mA$)?

When the transistor is used as an amplifier,

In an $n-p-n$ transistor,$200$ electrons enter the emitter in $10^{-8} \ s$. If $1 \%$ of electrons are lost in the base,then the current that enters the emitter and the current amplification factor are respectively $\left[e=1.6 \times 10^{-19} \ C\right]$