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3DQDVRQLF
1.5 Video amplifier and ABS
1.5.1 Video output amplification
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block diagram and functional description
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The video output amplification is performed by the TDA6106Q IC which is a monolithic amplifier. It can
be seen as an operational amplifier with negative feedback. The advantage of negative feedback is
that the amplifier characteristics do not play an important role up to certain frequencies.
• TDA6106Q pin 3 is the inverting input. The input stage (inside the TDA6106Q) consists of a bipolar
NPN transistor in a long tailed pair configuration
• TDA6106Q pin 8 is the cathode output pin This pin is connected to the CRT cathode via a high-
voltage flash-over protection resistor of 1.5k (R910, R9l1, R9l2)
• TDA6106Q pin 9 output is used for feedback to the negative input (pin3). This output also delivers
the transient currents far the video output voltage of 100Vpp with rise and fall times of 75ns. The
current is delivered by a quasi complementary class A/B push-pull stage designed in DMOS
technology The high frequency purl of the output signal at this pin is forced to the cathode output pin 8
with a coupling capacitor
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design considerations:
a - negative feedback amplifier basic design
The basic configuration of an amplifier with negative feedback is shown on the following figure 30.
3
R901
R904
R902
R905
R903
R906
Fig.29: Video amplification diagram
Z
i
V
i
Fig. 30: Basic video amplification
TDA6106Q
4
8
9
C907
C908
C909
100k
R907
R908
R909
Z
f
-
V
-
A
+
+
V
Z
a
32
R911
R912
R913
CRT
1.5k
CATHODE
V
o
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