Write the functions of three segments of a transistor

(i) Write the functions of three segments of a transistor.
(ii) Draw the circuit diagram for studying the input and output characteristics of n-p-n transistor in common emitter configuration. Using the circuit,explain how input, output characteristics are obtained.

(i) (a) The base of transistor is lightly doped i.e. the number density of majority carriers in the
base is always lesser as compared to emitter or
collector.
(b) The emitter supplies the majority carriers for
current flow.
(ii) n-p-n Transistor circuit diagram :