NJM2552V Ver la hoja de datos (PDF) - Japan Radio Corporation

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NJM2552V

100MHz INPUT MIXER AND 450kHz FM/AM IF DEMODULATOR IC

Japan Radio Corporation  

NJM2552

! Description

# AM AGC Line

1. Example of external circuit

R3

AM AF

OUT

20k AM AGC Line

C16

10u

+

20

19

18

17

16

15

14

AGC IN

AM

DET

M IXER

RSSI

FM AF

OUT

13

12

11

-A AMP

OSC

AMP

AGC

+

-

AM AMP

AM IF

+ FM AMP

FM

-

DET

1

2

3

4

5

6

7

8

9

10

CERAMIC

FILTER

2. 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.

# RF AGC Line

1. Example of external circuit

RF AGC Line

V++

VV++

RF IN

Tr2

Tr3

RF Amplifier

20

19

MIX IN

from IF Am p

18

V++

2k

17

16

RF AGC

OUT

Tr1

112207kk

2. 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.

Ver.2007-10-24

- 13 -

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