Working of transistor

The name of this electronic device is derived from it’s fundamental action transfer resistor.

There are four possible ways of biasing the two P-N junctions (emitter junction and collector junction) of transistor.

Active mode: Also known as linear mode operation.
Saturation mode: Maximum collector current flows and transistor acts as a closed switch from collector to emitter terminals.
Cut-off mode: Denotes operation like an open switch where only leakage current flows.
Inverse mode: The emitter and collector are inter changed.