Question

If both the junctions of a transistor are forward biased, then it will be in:

• A. Saturation mode
• B. Active mode
• C. Cutoff mode
• D. Inverse active mode

Hint:

Saturation mode: both junctions forward biased → transistor acts like a closed switch.

Answer 1

The Correct Option is A

To determine the operating mode of a transistor, we need to understand the biasing conditions of its junctions. A transistor typically has two junctions: the emitter-base junction (EBJ) and the collector-base junction (CBJ).

• Saturation Mode: Both the emitter-base junction and the collector-base junction are forward biased. In saturation mode, the transistor conducts maximum current from collector to emitter.
• Active Mode: The emitter-base junction is forward biased, while the collector-base junction is reverse biased. This is the mode where a transistor typically amplifies signals.
• Cutoff Mode: Both the emitter-base junction and the collector-base junction are reverse biased, and the transistor does not conduct. It's in the "off" state.
• Inverse Active Mode: The collector-base junction is forward biased, and the emitter-base junction is reverse biased, leading to reverse operations with degraded performance. This is rarely used purposely.

Given the problem statement and options, if both junctions of a transistor are forward biased, then the transistor will be in saturation mode. This is because the condition of both junctions being forward biased matches the criteria for saturation mode operation.