Samsung DVD-808K Service Manual page 87

Circuit Descriptions
7-5-3. Low pass filter VF1, VF2
VF1 and VF2 remove quantization noise occurring in the course of D/A conversion as low pass filter with
cut-off frequency of 6.75MHz. VR5 and VR6 are input impedances and convert the level of subcarrier.
GAIN(dB)
0(dB)
-3(dB)
7-5-4 Amplifier
VQ1 is buffer and the gain is amplified through VQ2, VQ3. The main factors which determine the gain are VR10
and VR11, and the gain is 1+VR11/VR10. VR12 is the main factor that determines the offset of output signal of
amplifier unit and the rate is approx. VR 12/(VR10+VR11)
Video input
7-6-5 Buffer
VQ4, VQ5, and VQ6 are buffer unit and circuit that double the drive power so as to output without signal conver-
sion when connected with exterior devices. VC11 is an AC coupling capacitor, VR19 is an essential impediance at
video signal interface and being matched with the impediance in the input block of exterior devices determines the
level of video signal.
7-22
6.75MHz
Fig. 7-40 Frequency features of VF1,VF2
+8V
VR9
VQ2
C1623
VR11
VR10
-8V
Fig. 7-41 Amplifier
+8V
VR12
VQ3
A812
Video output
Frequency
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