Pin Functions
Pin
No.
Symbol
Circuit Configuration
Description
1
FM DETECTOR
OUTPUT
Pin 1 is an audio FM output pin. A 100
resistor is connected in series with the
emitter follower.
(1)
Monaural applications
CR are used to form a de-emphasis
cicuit externally.
t = CR1
(2)
Audio multiplexing applications
Depending on the audio multiplexing
decoder application, the input
impedance is low, which may distort the
L-R signals, etc., and degrade the
stereo characteristics. In such an event,
add a resistor between pin 1 and GND.
R2
^ 5.1 k
2
FM AQT FILTER
GYLATOR
Pin 2 is the FM Automatic Quadrature
Tuning filter pin. This pin controls the
quadrature detector so that it remains at its
center frequency (4.5 MHz), and is the point
where the two control currents are added.
If the value of external capacitor C1 is small,
the low-range frequency characteristics
deteriorate. If the capacitance is too large,
the low-range characteristics improve, but
the response characteristics at SW-ON, etc.,
worsen.
The recommended value for C1 is 10 F to
33 F.
3
RF AGC OUTPUT
Pin 3 is the RF AGC output pin. It is an
emitter output, and a protective resistor of
200
is connected between pin 3 and
emitter.
This pin determines the resistance bleeder
(R1, R2) values according to the maximum
gain of the tuner.
Continued on next page.
LA7583
No.5177-7/16