Question

The active region of the output characteristics for a common base transistor is that in which _______.

• A. emitter junction is forward biased and collector junction is reverse biased
• B. both emitter and collector junctions are forward biased
• C. only collector junction is forward biased
• D. both emitter and collector junctions are reverse biased

Hint:

Active region in BJT means forward-biased emitter and reverse-biased collector junction.

Answer 1

The Correct Option is A

In any BJT, for proper amplification (i.e., active mode), the transistor must satisfy:
\[ \text{Emitter-Base junction: Forward biased} \\ \text{Collector-Base junction: Reverse biased} \]

Why?
Forward bias allows carriers to be injected into the base.
Reverse bias on the collector junction allows collection of minority carriers.

In common base configuration:
Input: Emitter to Base
Output: Collector to Base

Hence, option (1) is the correct operational bias condition.