LA1260

No.1506-4/14

How to apply FM AFC

The S curve at the FM output pin (pin 8) is as shown in Figure 1. Therefore, the domestic (Japan) band (lower local

oscillation) use and foreign band (upper local oscillation) use differ as shown in Figures 2 and 3.

AM local oscillation

Since the LA1260 contains an ALC circuit, the oscillation level at pin 16 can be limited to 60 to 150mV in the

following applications where a coil is used.

Stable oscillation occurs at a coil impedance of 5k

Ω or greater viewed from across pins 16 and 15. Turn ratio n and

greater for SW use.

If turn ratio n is increased more than needed, the oscillation level at pin 16

drops, thereby lowering the maximum sensitivity as shown in Figure 5 and 6.

Figure 7 shows the relation between turn ratio n and oscillation level at pin

16 in the MW band.

Unit (capacitance : F)

Figure 1

Figure 2 Domestic (lower local

oscillation) band

Figure 3 Foreign (upper local

oscillation) band

Unit (resistance :

Ω, capacitance : F)

Unit (capacitance : F)

OSC injection voltage at pin 16 – mV

OSC injection voltage at pin 16 – mV

21MHz reception mode

Maximum sensitivity

(input at detection

output –30dBm)

Maximum sensitivity

(input at detection

output –30dBm)

Usable sensitivity (S/N=20dB)

Usable sensitivity

(S/N=20dB)

Figure 5

Figure 6

Figure 4