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Question

A PNP transistor is operating in active region. If the emitter voltage decreases such that the emitter becomes less positive than the base while the biasing condition of the collector-base junction remains unchanged, the transistor will enter _______.

This question was previously asked in
RRB JE 2025 CBT 2 Mechanical and Allied Engg Question Paper English (2-Jul-2026) (Shift-1)
The correct answer is

Cut-off region

To solve this question, we need to understand the operating regions of a PNP transistor and how changes in voltages affect these regions.

PNP Transistor Basic Operation

A PNP transistor in active mode typically has the emitter-base junction forward-biased and the collector-base junction reverse-biased. These conditions facilitate amplification.

  • Active Region: Emitter-Base junction is forward-biased, Collector-Base junction is reverse-biased. The transistor amplifies the input signal.
  • Cut-off Region: Both the Emitter-Base and Collector-Base junctions are reverse-biased. The transistor is effectively off, with no current flowing through.
  • Saturation Region: Both junctions are forward-biased. The transistor conducts maximum current, but there's no amplification.
  • Reverse Active Region: Emitter-Base junction is reverse-biased, Collector-Base junction is forward-biased. This is an unusual mode, with reverse direction current flow.

Analysis of Given Situation

The question states: "If the emitter voltage decreases such that the emitter becomes less positive than the base while the biasing condition of the collector-base junction remains unchanged."

This suggests that the forward-bias condition of the emitter-base junction is lost. With the emitter becoming less positive relative to the base, the emitter-base junction can become reverse-biased. Since the collector-base junction is mentioned to remain unchanged, it stays reverse-biased.

Conclusion

With both the emitter-base and collector-base junctions reverse-biased, the PNP transistor enters the Cut-off Region.

Therefore, the correct answer is: Cut-off region.

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Similar Questions

  1. A PNP transistor is fabricated with an increased base doping concentration while keeping all other physical dimensions and doping levels constant. What is the effect on the transistor's performance?

  2. In a properly biased PNP transistor operating in active region, the emitter terminal is _______.


Important Questions from Bipolar Junction Transistor

  1. Photo transistor is used for:

  2. What happens if a voltage of about 0.7 V is applied across the base and emitter of the NPN transistor?

  3. In a junction transistor, recombination of electrons and holes occurs in

  4. A bipolar junction common emitter transistor is operating in saturation mode, identify the correct statement.

  5. In BJT when both the junctions are forward biased, then its operating mode is called:

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