LA7555 View Datasheet(PDF) - SANYO -> Panasonic
Part Name
Description
Manufacturer
LA7555 Datasheet PDF : 11 Pages
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LA7555
4. Lock detector
As shown in Fig.4-1, the lock detector is an APC time constant switching detection circuit which expands the APC
pull-in range. The detection circuit operates by the OR of the IF AGC voltage and the video signal. The weak field
is detected by the IF AGC voltage and the unlock state when detuned is detected from the video signal.
Fig.4-1
5. AGC detector
As shown in Fig.5-1, the AGC detector is equipped with a noise canceller function which prevents malfunction of
the AGC system. The AGC detection output (pin 13) is also used for video output, FM detection output, and as the
simultaneous mute (AV MUTE) pin.
Fig.5-1
6. RF AGC
As shown in Fig.6-1, the RF AGC controls the gain of the tuner’s RF amplifier. Measurement is made whether the
region is snow region (noise on the screen, poor S/N ratio) or a saturation region (contours can be clearly seen but
look bad due to video signal distortion), and the RF AGC delay point is set as shown in Fig6-2. Pin 10 is also used
for video output, FM detection output, and as the simultaneous mute (AV MUTE) pin.
Fig.6-1
Fig.6-2
No.2927–6/11
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