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Question 13.3: Determining the Operating Region of a BJT A given npn transi...

Determining the Operating Region of a BJT
A given npn transistor has β = 100. Determine the region of operation if a. IB = 50 μA and IC = 3mA; b. IB = 50 μA and VCE = 5V; c. VBE = -2 V and VCE = -1V.

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a. Since IB and IC are positive, the transistor is either in the active or saturation region. The constraint for saturation

βIB > IC

is met, so the device is in saturation.

b. Since we have IB > 0 and VCE > 0.2, the transistor is in the active region.
c. We have VBE < 0 and VBC = VBE – VCE = -1 < 0. Therefore, both junctions are reverse biased, and operation is in the cutoff region.

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