LA7577 查看數據表（PDF） - SANYO -> Panasonic
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LA7577 Datasheet PDF : 16 Pages
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LA7577N
RF AGC Variable Resistor (Pin 4)
The operating point of the RF AGC can be adjusted using
a variable resistor connected to pin 4 as shown in Figure
11. When pin 4 is pulled to 0.5V or lower, both the FM
and video outputs are muted.
Figure 13. 1st SIF stage
Figure 11. RF AGC adjustment
VIF Input (Pins 5 and 6)
The VIF amplifier inputs on pins 5 and 6 should be capac-
itively coupled to block DC. The input signal is the aver-
age of the signals on these inputs. The input resistance is
approximately 1.5kΩ and the input capacitance is approxi-
mately 3pF.
Figure 14. SAW filter matching
RF AGC Output (Pin 10)
The RF AGC output on pin 10 is an emitter follower with a
200Ω series protection resistor as shown in Figure 15. The
value of the bleeder resistor connected between pin 10 and
the tuner, shown in Figure 16, should be chosen based on
the tuner maximum gain.
Figure 12. VIF stage
1st SIF Input (Pin 8)
The 1st SIF amplifier input on pin 8, shown in Figure 13,
should be capacitively coupled to block DC. If a SAW fil-
ter is used, an inductor should also be connected as shown
in Figure 14. This matches the SAW filter output capaci-
tance to the LA7577N input capacitance and increases the
sensitivity. The inductor typically would be 0.62µH (for
Japan), 1.0µH (for the USA) or 1.3µH (for PAL countries).
Figure 15. RF AGC output
Figure 16. Bleeder resistor connection
No. 4037—10/16
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