LA1787M Datasheet, PDF (24/54 Pages) Sanyo Semicon Device – Single-Chip Tuner IC for Car Radios

LA1787M
(4) Stereo indicator sensitivity improvement
The stereo indicator sensitivity (on/off) is equivalent to that of the LA1780M
Stereo on level
Stereo off level
LA1781M/1784M
4.1%
3.1%
LA1787M/1780M
2.6%
1.6%
(Typical value)
*: The pilot level such that the stereo indicator goes on or off for a 10.7 MHz unmodulated IF input.
(5) FM oscillator circuit removed
The internal FM oscillator circuit provided in the LA1781M has been removed. The FM oscillator level can be
adjusted by constructing an external circuit block.
*: However, this requires 4 more external parts than the LA1781M: 1 transistor and 3 resistors/capacitors.
VCC
IC internal
VCC
IC internal
VCC
4
4
Vt
Vt
LA1787M/1784M FM OSC
A13600
LA1780M/1781M FM OSC
A13601
3. Gain distribution
The table below shows the gain distribution of the LA1780M, LA1784M, and LA1787M. (These are measured
values.) Compared to the LA1784M, the total gain is lower.
LA1780M
LA1784M
LA1787M
First mixer
First IF amplifier
Second mixer
Second IF amplifier
1st MIX (10.7)
10 dB
7.5 dB
7.5 dB
1st IF (10.7)
3.3 dB
13 dB
3.5 dB
2nd MIX (450)
3.2 dB
7 dB
8.6 dB
2nd IF (450)
69 dB
66 dB
67 dB
: No circuit changes from the LA1784M.
: Equivalent to the LA1780M circuit. (The gain is lower than that in the LA1781M and LA1784M.)
: The mixer circuit has been modified to improve adjacent channel suppression and interference.
: Equivalent to the LA1780M circuit.
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