-
11
-
Model No.: 14LAANZACDC
Version: 1.0
In the IF filtering circuit V101, VD101, R116, R117, R106, R112 and R115 are formed into an IF
absorption selection circuit, which is controlled by the level from N701’s Pin15 output high level,
V101 saturates and conducts, and R106 is integrated into the paralleled resonator comprising
R112 and VD101, by which the resonating frequency dot is moved to low frequency section and
IF and amplitude frequency characteristics are stretched. In this case, IF characteristics are
stretched. In this case, IF characteristics include B/G, I and D/K SIF characteristics. When Pin15
output low level, V101 cuts off and VD101 is not integrated into the paralleled resonator, by
which the resonating frequency dot is moved to high frequency section and IF and amplitude
frequency characteristics are narrowed. In this case, IF characteristic includes M SIF
characteristic.
In the IF pre-amplifier, R108, R109 and R111 are bias resistors of V102, R107 and C111 are
formed into a decoupling filter circuit, R110 is a damping resistor to stretch frequency band of
the amplifier.
2. VIDEO
SIGNAL
PROCESSOR
The video signal processor in LA76818A mainly consist of an AV switch and filtering circuit,
luminance signal processor, chroma signal processing/ color decoding /RGB selection circuit,
which is mainly used to complete all video signal processes and demodulate out three primary
color signals R, G, and B.
a) TV /AV switch circuit in LA76818A is used for switching over TV video signals,
AV video signals, Y/C signals from the S-VHS terminal. The filtering circuit is used
for strobe, delay, sharpness control, black level stretching for Y signal and strobe,
amplification, color saturation control and color killing control for C signal.
The video signals from LA76818A’s Pin46 are coupled by C204 to Pin44. External
video signals from the AV terminals are coupled by C211 to Pin42. After clamped,
DC video signals are restored and sent into the TV /AV switch circuit to select out
one set of video signals from the internal video signals under the control of the I
2
C
bus. Then the set of video signals are output in three ways. One set is output from
LA76818A’s Pin40 and sent to the video output terminal after divided by R802 and
E804, buffered by V801 and coupled by C805 to provide video signal source for the
monitor. Another two sets of signals are sent to the filtering circuit for Y /C
separation.
