0
1.1kviews
For the given two stage circuit find Ri, Ro and voltage gain. Given β1=β2=220
1 Answer
0
0views

enter image description here

Since β is mentioned use re-model. First carry out dc analysis for Ie1 and Ie2, so all connected capacitors acts as open circuit. Hence circuit becomes,

enter image description here

As β1=β2=220, then Ie1 will be equal to Ie2

By Voltage divider rule,

VR2=R2R1+R2Vcc

VR2=2.2K22K+2.2K×15

VR2=1.36V

By KVL,

VR2VBE=VE1

1.36V0.7V=VE1

Let,VBE=0.7V

VE1=0.663V

Ie1=VE1Re1=0.663V150Ω

Ie1=4.424mA

As stage 1 and stage 2 are identical & value ofβ1=β2=220

Ie1=Ie2=4.424mA

AC equivalent of the circuit becomes,

enter image description here

Rin (Input Resistance):

Rin=R1||R2||βre

re=26mVIe1=26mV4.424mA

re=5.87Ω

Hence, Rin becomes

Rin=22k||2.2k||220×5.87

Rin=0.784kΩ

Ro(Output Resistance):

Ro=Rc2s=1kΩ

Av (Voltage Gain):

Av2=VoVo1=Rc2re

Av2=1kΩ5.87Ω

Av2=-170.35

Av1=(Rc1||Rin2)re

But, Rin2=R3||R4||βre=0.784kΩ

Av1=(1kΩ||0.784kΩ)5.87Ω

Av1=-74.865

So Av is obtained by multiplying Av1 and Av2,

Av=Av1×Av2

Av=(170.35×74.865)

Av=12753.25

Please log in to add an answer.