LA1266

No.2291-4/11

2. AM/FM changeover

• AM/FM changeover is made using pin 20 as shown right.

the range of +0.1V to – 0.8V. If not within this range, distortion and

selectivity will get worse. A resistance of 68k

Ω at the IFT cold terminal,

which is used to prevent the changeover circuit from malfunctioning,

must be connected.

3. Local OSC buffer output

• When local OSC buffer output waveform is saw-toothed at the SW mode, connect a reistance of 1.2k

Ω or

thereabouts across pin 24 and GND.

4. Capacitance across pin 9 and GND

A large capacitance across pin 9 and GND may cause a

misstop at an adjacent channel when the channel select

speed is made faster at the autmatic channel select mode.

In thes case, decrease the capacitance across pin 9 and

GND.

However, if too decreased, the LED will flutter at low

modulation frequencies at the time of detuning.

Therefore, it is recommended to fix the capacitance

across pin 9 and GND to be 3.3µF to 10µF.

The relation between modulation frequency and

demodulation output voltage on pin 9 with the

capacitance across pin 9 and GND as a parameter is

shown right.

5. If the coupling coefficient of the local OSC coil is small and an antiresonance point of approximately 100MHz is

present or the stray capacitance across pin 24 and pin 23 is large, a parasitic oscillation of approximately 100MHz

may occur in the buffer output (pin 24). In this case, connect a capacitance of approximately 30pF across pin 24 and

GND.

6. AM OSC coil

Generally speaking, the following should be noted. Avoid winding with loose coupling between primary side and

secondary side (especially SW1, SW2). To be concrete, the pot core type is better than the screw type which is loose

in coupling. This prevents the local OSC frequency from turning third

resonance frequency related to the coupling coefficient.

If pin 8 is used for stop signal (SD) only, without using LED, it is

100k

Ω.

8. To prevent whistle from worsening, make the pattern of AM output pin 15 as

short as possible.

9. AM, FM IF buffer output

Application of a voltage to pin 13 (STRQ) causes AM IF(455kHz) signal (at AM mode) and FM IF(10.7MHz) signal

(at FM mode) to be delivered at pin 11 and pin 10, respectively. It is recommended that the voltage to be applied to

68k

Ω

V9 – Modulation Frequency

Modulatin frequency

Ω