For a transistor to act as a switch, it must be operated in
- (A)Active region
- (B)Saturation state only
- (C)Cut-off state only
- (D)Saturation and cut-off state✓ Correct
Answer: (D)
Solution
A transistor acts as a switch by operating in two extreme states:
The active region is used for amplification, not switching, as the transistor operates in a linear mode between cut-off and saturation.
Therefore, for switching applications, the transistor must operate in both saturation and cut-off states.
- Cut-off state: The transistor is OFF (no current flows from collector to emitter). This represents the "open switch" or logic 0 state.
- Saturation state: The transistor is fully ON (maximum current flows from collector to emitter with minimum voltage drop). This represents the "closed switch" or logic 1 state.
The active region is used for amplification, not switching, as the transistor operates in a linear mode between cut-off and saturation.
Therefore, for switching applications, the transistor must operate in both saturation and cut-off states.
JEE Main · 2022 · 27 Jun 2022 · Shift 2 · Single correct option