LA3335M Datasheet, PDF (4/6 Pages) Sanyo Semicon Device – PLL FM Multiplex Demodulator for 3 V Headphone Stereos and Radio-cassette Recorders

LA3335M
b) Connect the connection point of the semifixed resistor connected to pin 4 and the fixed resistor to a frequency counter
through the R_X of 240 kΩ. Fig. 2 shows how the error changes as the R_X value is decreased.
∆F – R_X
R_X – Ω
Figure 2
3. Separation setting mothod
The LA3335M is so designed that the sub-signal gain is approximately 1.25 times as high as the main signal gain. The
separation can be set by attenuating the sub-signal of the FM detection output. (See Figure 3)
Ro 6 Output impedance
Figure 3
The value of capacitor Co depends on the attenuation of the sub-signal of the FM detection output and the IF IC output
impedance Ro. Fig. 4 shows the value of separation setting capacitor Co when Ro is set to 3 kΩ.
For example, when the attenuation of sub-signal of the IF IC output is 0.9 time that of the main signal, it is seen from
Figure 4 that the value of Co is approximately 500 pF.
Co – Attenuation
Vs = Sub-signal peak value
Vm = main signal peak value
Separation : 35 to 40 dB,
set to double hump response.
Input sub-signal attenuation, m – dB
Figure 4
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