Q7Basic Electrical Engineering
Question
2 marks
What is BJT?
Answer
A Bipolar Junction Transistor (BJT) is a three-terminal, current-controlled semiconductor device used extensively for electronic switching and signal amplification.
A BJT is formed by joining three layers of P-type and N-type semiconductor materials, creating two PN junctions (forming either an NPN or PNP structure). The three terminals are the Emitter (heavily doped), the Base (very thin and lightly doped), and the Collector (moderately doped).
It is a current-controlled device because a tiny current injected into the Base terminal exerts total control over a significantly larger current flowing between the Collector and Emitter terminals, enabling high-gain amplification.