An oscillator is nothing but an amplifier with

In $n-p-n$ transistor, in $CE$ configuration:

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

In a junction transistor, the collector current changes by $6.8 \,mA$, if the emitter current is changed by $7 \,mA$. For such a transistor, the current amplification factor is

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

The value of $I_c$ for the configuration shown is in $mA$.