Question

In the given circuit, using a silicon BJT, what is the value of VCE?

(a) 20 V

(b) 15.52 V

(c) 14.98 V

(d) 13.97 V

The question was posed to me in a national level competition.

My enquiry is from BJT DC biasing topic in portion BJT Biasing of Analog Circuits

Answer 1

Correct answer is (b) 15.52 V

The explanation is: Consider the BJT to be in saturation. Then IC=20-0.2/2k=9.9 mA

And IB=20-0.8/430k=0.044 mA

IBMIN=ICSAT/β=5.09/50=0.198mA which is greater than above IB.

Hence transistor is in the active region.

Thus IC=βIB.

VBE=0.7V

IB=20-0.7/430=44.88μA

IC=50×44.88=2.24 mA

VCE=20-2.24*2=15.52V.