Question

From the given circuit, using a silicon BJT, what is the value of VCEQ?

(a) 7 V

(b) 0.7 V

(c) 6.83 V

(d) 7.17 V

This question was addressed to me during an online exam.

Origin of the question is BJT DC biasing topic in division BJT Biasing of Analog Circuits

Answer 1

The correct choice is (c) 6.83 V

To explain I would say: Consider the BJT to be in saturation. Then IC=12-0.2/2.2k=5.36 mA

And IB=12-0.8/240k=0.047 mA

IBMIN=ICSAT/β=5.09/50=0.1072mA which is greater than above IB.

Hence transistor is in the active region.

Thus IC=βIB.

VBE=0.7V

IB=12-0.7/240=47.08μA

IC=50×47.08=2.354 mA

VCE=VCC-ICRC=12-2.354*2.2=12-5.178=6.83V.