LA1781M_09 Datasheet, PDF (33/48 Pages) Sanyo Semicon Device – For Car Radios Single-Chip Tuner IC

LA1781M
R36-37
Open
10kΩ
Detector output
MPX OUT
VO
330mVrms
280mVrms
Pin 36 AC level
QDIN
235mVrms
200mVrms
• Band Muting Adjustment Procedure
The muting bandwidth can be modified as shown in figure 31 with the resistor RBW between pin 34 and 37.
RBW -- Muting Bandwidth Fig. 31
280
RBW
+
+
240
1μF
0.47μF
SA208
200
10kΩ
Sumida
37 36 35 34
160
ANT IN 98MHz 100dBμ
120
80
40
0
1.0
2 3 5 7 ₁₀
2 3 5 7 ₁₀₀
2
Resistor RBW between pins 34 and 37 -- kΩ
6. AM
• AM AGC system
The LA1781M RF AGC circuit takes its input from three sources : the WIDE AGC pin (pin 46), the MIDDLE AGC
pin (pin 49) and NARROW AGC. There is also an IF AGC circuit.
RW
1st MIX 10.7MHz CF
2nd MIX 450kHz CF
IF Amp.
DET
RF
62
49
52
31
1st OSC
X'tal
46
Middle AGC IN
Wide AGC IN
ANT
DUMPING
RF AGC
Narrow AGC IN
Amp.
IF AGC
VCC
42
240kΩ
VCC
44
2.2μF
57
+
47μF
48
+
3.3μF
Fig. 32
No.6038-33/48