NJM2552 JRC, NJM2552 Datasheet - Page 13

• Manufacturer Part Number: NJM2552
• Description: FM IF Demodulator IC / SSOP20
• Manufacturer: JRC

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Ver.2006-11-06
Description
AM AGC Line
1.
2.
RF AGC Line
1.
2.
Example of external circuit
Explanation
AM AGC IN terminal (pin18) is usually connected with the AM DET terminal (pin 14) through the ripple
filter of R3 and C16. This filter has the time constant of R3xC16 and this value of time constant is generally
selected to be 5 to 10 times larger than the lowest cycle of the AM modulation signal (, not AM
demodulated signal). AGC IN terminal (pin 18) can also be controlled by an external DC source instead of
DC output of AM DET terminal.
Example of external circuit
Explanation
RF AGC OUT terminal (pin17) can be connected to the bias circuit of the external RF amplifier to control
its gain. RF AGC characteristics are shown on following page.
20
1
19
2
C16
10u
AMP
OSC
MIXER
+
18
3
AGC IN
RF IN
20k
R3
AGC
RF Amplifier
17
4
AM AGC Line
+ -
CERAMIC
FILTER
Tr3
16
AM AMP
5
AM IF
RF AGC Line
AM AF
V+
OUT
RSSI
15
6
DET
AM
14
7
MIX IN
from IF Am p
20
+
-
13
8
19
FM AMP
-A
12
9
AMP
NJM2552
18
Tr1
127k
FM AF
2k
V+
OUT
V+
10
11
Tr2
DET
FM
17
RF AGC
OUT
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