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The signal gain : G =
Generally, at low frequencies, A(p) >>
G =
For this formula, we can define :
* Attenuation factor d(p)=
* Feedback factor K(p)=
b – Z-421 implementation
• Zi impedance consists of input resistors connected between TDA6106Q pin 3 and the TDA8844
output : R90l, R902, R903 and R520, R521, R522.
• Za impedance consists of bias resistors : R904, R905, R906 arid parasitic capacitance Ca which
appears between TDA6106Q input and ground.
• Zf impedance consists of feedback resistors : R907, R908, R909 and parasitic capacitance Cf which
appears between TDA6106Q input and output.
Then we can summaries the video amplifier function with the following figure 31
R511
R512
11
R513
12
13
−
Vo p
( )
d p A p
( ) ( )
=
+
1
A p K p
( ) ( )
Vi p
( )
1
is valid, we can approximate this formula
K p ( )
d p
( )
Zf
−
= −
K p
( )
Zi
−
V
( )
p
−
V p
( )
i
Z
=
Z
f
−
V
( )
p
−
V p
( )
o
Z
/ /
i
=
Z
/ /
Z
i
R901
R902
R903
C
a
R904
R905
R906
V
( )
p
+
at V
(p)=0
o
/ /
Z
f
a
+
/ /
Z
Z
a
i
V
( )
p
+
at V
(p)=0
i
Z
a
+
Z
a
f
C
f
R907
R908
R909
-
V
-
A
+
+
V
Fig. 31
33
3DQDVRQLF
V
output
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