State three operating regions of the transistor

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 (I) Active region : EB junction is forward biased and CB junction is reversed biased. Transistor in this region operates as an amplifier.

(II) Saturation region : Both junctions of the transistor are forward biased. In this state transistor behaves as a close switch.

(III) Cut-off region : Occurs when both junctions of the transistor are reverse biased. In this state transistor behaves as an open switch.

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