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AMPLIFICADORES
+
VI = VS + VG
-
(S N ) = VV
VI
VG
VS
IS
=
I
IG
VS
VS
VG
+
VIS = VS
-
VG = 0
VI
VG
VS
RC1
VS
RC2
VI
VG
V I G = V G' ⋅
V G' = V G ⋅
zs
RI
-
zs
V IS = V S ⋅
+
RC1
VG
(Z S
RI
// R C 2 ) + R C 1 + R I
(Z S
RI
// R C 2 ) + R C 1 + R I
RC 2
RC 2 + Z S
RC2
RI
VI
V2
+
Vi2
Vi1
+
Vd/2
Vo2
-
+
Vc
Vo1
+
Vd/2
V1
V d = V 2 − V1 ; Vc =
V2 + V1
2
Vo2
Vi2
Vod = ADD ⋅ Vid + ADC ⋅ Vic
A
Vi1
Voc = ACD ⋅ Vid + ACC ⋅ Vic
Vo1
CM RR =
E =
ADD
ADC
AC D
ADD
Vic 

Vod = ADD Vid +

CMRR 

EN UN AMPLIFICADOR “SINGLE ENDED” (Vo1= 0) SOLO ESTÁN
DEFINIDAS ADD Y ADC.
V0 = AD ⋅Vid + AC ⋅Vic
AMPLIFICADORES DE INSTRUMENTACIÓN
v1
R2
+
-
RG
v2
R1
+
R
R
vo
R3
 R   2R 
VO = (V2 − V1 )  2  
+ 1
 R1  RG

R2 R4
=
R1 R3
R4
+
RG
R4
R3
+
+
v1
R2
R1
vo
 R
R 
VO = (V2 − V1 ) 1 + 2 + 2 2 
R1
RG 

R1 = R3 ; R2 = R4
v2
R2
v1
R1
+
v2
R3
vo V = (V − V ) ⋅ R2
2
1
O
R1
R4
R2 R4
=
(0,1% ⇒ CMRR ≤ 66 db)
R1 R3
EJEMPLO: PUENTES DE MEDIDA
V
R4
R3
R1 
 R2
V =
−
V =
 R 2 + R3 R1 + R 4 
o
Vo
R2
R1
Si
Si
y
R 4 R3
−
R1 R 2
V
=
 R 4  R3 

1 +
1 +
R
R
1
2



R 4 R3
=
R1 R 2
V =0
o
R1= R2= R4= R (un solo elemento variable)
R3=R(1+ δ)
V =
o
Si
y
δV
2(2 + δ )
R2= R4= R
R1= R3= R(1+δ) (mayor sensibilidad)
1 − (1 + δ )
2δ
V =
V≅
V
(2 + δ )
δ +1
2
2
o
Si R1= R4= R
y R2= R(1+δ)
R3= R(1-δ)
δ
V = V
2
o
CIRCUITO EQUIVALENTE.
R2
2
Vd
R
R1
R
V
1
2
R
1
Vc
R(1 + δ )
V δ
2 (2 + δ )
V
Vc =
2
Vd =
R1 =
R
2
R2 = R
1+ δ
1− δ
R2
2
+
R (1 − δ )
R (1 + δ )
1
2
V
Vd
+
Vc
Vd
R1
1
R (1 + δ )
R (1 − δ )
V
δ
2
V
Vc =
2
Vd =
(1 − δ )
2
R1 = R 2 =
2