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TBA120S<br />

INTEGRATED FM/IF<br />

AMPLIFIER AND DEMODULATOR<br />

Fig. 2': Operating circuit using<br />

a ceramic filter (Murata)<br />

dB<br />

120 +15V 100<br />

+~<br />

AF<br />

1:<br />

.' ..<br />

90<br />

so<br />

"<br />

30<br />

20<br />

10<br />

V<br />

V V<br />

/ V -<br />

l-t-:'" I<br />

, . .<br />

O~ O·<br />

! I<br />

TBA'20S<br />

.!f.tSQkHz<br />

m.)O'"<br />

'.v" kHz<br />

V",,2V<br />

./ dl.t25kHz<br />

-v.<br />

V r--- m.SO"l.<br />

I<br />

'",(""kHz<br />

VI/·12V<br />

J 1-- 1-<br />

I<br />

•<br />

0<br />

•<br />

Fig. 3: AM rejection ratio versus input voltage<br />

!<br />

I<br />

'm'<br />

For good far-<strong>of</strong>f selectivity the ceramic filter<br />

should be combined with an LC filter.<br />

Frequency Filter Resistor R<br />

10.7 MHz<br />

S.SMHz<br />

4.5 MHz<br />

SFC 10.7 MA 300 ... 390 Q<br />

SFC 5.5MA 560 ... 680 Q<br />

SFC 4.5MA 1000 ... 1200 Q,<br />

Fig.4: Internal circuitry<br />

14<br />

I 2<br />

610137<br />

8-33

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