Which of these is a unipolar transistor?

According to a graph drawn between the input and output voltages of a transistor connected in common emitter configuration, the region in which the transistor acts as a switch is

For a transistor,the current amplification factor is $\alpha = 0.8$. The transistor is connected in a common emitter configuration. The change in the collector current when the base current changes by $6 \, mA$ is.....$mA$.

$A$ transistor is connected in a common emitter configuration with $R_o = 4 \text{ k}\Omega$,$R_i = 1 \text{ k}\Omega$,$I_C = 1 \text{ mA}$,and $I_b = 20 \text{ }\mu\text{A}$. The voltage gain is:

An oscillator is nothing but an amplifier with

In a common base amplifier,the phase difference between the input signal voltage and the output voltage is