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For a narrow base PNP BJT, the excess minority carrier concentrations (ΔnE for emitter, ΔpB for base, ΔnC for collector) normalized to equilibrium minority carrier concentrations (nE0 for emitter, pB0 for base, nC0 for collector) in the quasi-neutral emitter, base and collector regions are shown below. Which one of the following biasing modes is the transistor operating in?

For a narrow base PNP BJT, the excess minority carrier concentrations (ΔnE for emitter, ΔpB for base, ΔnC for collector) normalized to equilibrium minority carrier concentrations (nE0 for emitter, pB0 for base, nC0 for collector) in the quasi-neutral emitter, base and collector regions are shown below. Which one of the following biasing modes is the transistor operating in? Correct Answer Inverse active

Observation 1:

Consider the hole concertation in the base, near the collector-base junction.

Minority carrier concertation (∆pb) is high. This is because excess holes are supplied by the collector (P).

This means C.B. Junction is forward Biased.

Observation 2:

The minority hole carrier concertation in a base region near the Emitter – base Junction is low, i.e. holes are extracted from the base.

This indicates that the Emitter Base junction is Reversed Biased.

∴ The mode of operation is Reverse Active.

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