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For the given circuit find Icq, VCEq, Vc & Ve.

enter image description here

Mumbai University > Electronics Engineering > Sem 4 > Discrete Electronic Circuits

Marks: 10M

Year: Dec 2016

1 Answer
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Given: β = 100, Vbe = 0.7V

For DC analysis, all the coupling capacitor acts as open circuit as shown in below circuit diagram. We need to find equivalent circuit at base terminal (Rth & Vth).

enter image description here

Figure 1: Circuit diagram without coupling capacitor and equivalent circuit diagram

Vth can be found using voltage divider method:

Vth=10×12.2k12.2k+56k

Vth=1.78V

Rth=12..2k||56k=10.01kΩ

Apply KVL from base to emitter junction,

VthRthIBVbeREIE=0 ----(1)

where IE=IC+IB=βIB+IB=IB(1+β)

Substitute in equation (1)

VthRthIBVbeREIB(1+β)=0

IB=VthVbeRth+RE(1+β)

IB=1.780.710.01k+(1+100)0.4k

IB=21.42μA

Icq=βIB=100×21.42μA

Icq=2.142mA

Apply KVL from Vcc to Ground through collector to emitter,

VccICRCVceqIERE=0 ----(2)

IE=IB+IC=2.142mA+21.42μA

IE=2.16mA

Substitute IE value in equation (2),

VccICRCIERE=Vceq

102kΩ×2.142mA2.16mA×0.4kΩ=Vceq

Vceq=4.852V

VC=VccICRC

VC=102.142mA×2kΩ=5.716V

VE=IERE=2.16mA×0.4kΩ=0.864

Answers:

  1. Icq=2.142mA
  2. Vceq=4.852V
  3. VC=5.716V
  4. VE=0.864V
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