Question

Is bipolar junction transistor is a voltage controlled device

Answer 1

Bipolar Junction Transistor (BJT) is a current controlled device as the collector's current is fully controlled by the base current.

The relationship between the current in the base, collector and emitter is given as

$I_e=I_b+I_c\\ I_c=\beta{I_b}\\ I_c=\alpha{I_e}$

Where $\alpha$ and $\beta$ are the gain of the Transistor in common emitter and common base mode respectively