Page 10 - Semester-IV-Electronics

 The output signal depends on the mean level of v & v ,
1 2

 v = (1/2)*(v + v ) ---- Common Mode Signal
c 1 2

 Difference Signal, v = (v – v )
d 1 2

 If in the absence of second signal, the gain for the first signal is A and
1
in the absence of first signal, the gain for second signal is A , then by
2
principle of superposition, in the presence of both the signals, the
output signal will be, v = A v + A v
1 1
2 2
0
 v = (v – v )
2
d
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 Also, 2v = (v + v )
1
c
2
 Hence, v = (v + 2v )/2 = v + (1/2)*v d
c
c
1
d
 And, v = (2v – v )/2 = v - (1/2)*v d
c
c
2
d
 So that, v = A [v + (1/2)v ] + A [v – (1/2)v ]
0
2
c
d
1
c
d
= (1/2)(A – A )v + (A + A )v c
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2
d
2
1
= A v + A v 10
d d
c c