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Analog circuits miscellaneous

  1. The common emitter forward current gain of the transistor shown is βF = 100.

    The transistor is operating in
    1. Saturation region
    2. Cut-off region
    3. Reverse active region
    4. Forward active region
Correct Option: C


Assume VBE = 0.7 and since β >> 1, IC ≈ IE
using KVL in base-emitter circuit,
10 – VBE – I ERE – IBRB = 0
⇒ 10 – 0.7 = (β + 1) IB. RE + RB. IB

⇒ IB =
9.3
mA = 0.025 mA
101 + 270

Now, using KVL in Collector-emitter circuit,
10 – VCE – (IE + IC)1 = 0 [Assume VCE = 0.2 V]
9.8
= IC ⇒ IC = 4.9 mA
2

(IB)min =
IC
=
4.9
= 0.049 mA
β100

As (IB)min < IB = 0.025 mA, therefore transistor operates in active region.



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