To use a transistor as an amplifier,

The base current in a transistor circuit changes from $45 \mu A$ to $140 \mu A$. Accordingly,the collector current changes from $0.2 \text{ mA}$ to $4.0 \text{ mA}$. The gain in current is

When an $n-p-n$ junction transistor is used as an amplifier in common emitter mode,

In an $NPN$ transistor,the collector current is $24 \, mA$. If $80\%$ of electrons reach the collector,its base current in $mA$ is:

$A$ $N-P-N$ transistor is connected in common emitter configuration (see figure) in which the collector voltage drop across the load resistance $(800 \; \Omega)$ connected to the collector circuit is $0.8 \; V$. The collector current is .............. $mA$.

$A$ common emitter amplifier circuit,built using an $npn$ transistor,is shown in the figure. Its $dc$ current gain is $250$,$R_C = 1\,k\Omega$ and $V_{CC} = 10\,V$. What is the minimum base current for $V_{CE}$ to reach saturation? (in $\mu A$)