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

  2. 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?


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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