Question

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

(a) 2.01 V

(b) 0.28 V

(c) 0 V

(d) 2.28 V

The question was posed to me by my college professor while I was bunking the class.

The question is from BJT DC biasing topic in portion BJT Biasing of Analog Circuits

Answer 1

The correct option is (d) 2.28 V

For explanation: 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

VE=IERE=(1+β)IBRE=51*44.88*1=2.28V.