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參數資料
| 型號： | LA7577N |
| 元件分類： | 接收器 |
| 英文描述： | FM, AUDIO SINGLE CHIP RECEIVER, PDIP24 |
| 封裝： | DIP-24 |
| 文件頁數： | 15/16頁 |
| 文件大小： | 354K |
| 代理商： | LA7577N |
LA7577N
No. 4037—8/16
This phase distortion is the cause of audio buzz, or
Nyquist buzz, because the VCO synchronizes to the com-
posite vector. A Nyquist buzz cancelation circuit is incor-
porated into the LA7577N to reduce the level of this noise
as shown in Figure 3.
A typical signal with Nyquist buzz is shown in Figure 4
together with the compensating signal generated by the
Nyquist-slope canceler and the resultant signal.
Figure 3. PLL detector with buzz cancelation
Figure 4. Nyquist buzz cancelation waveforms
The circuit shown in Figure 3 is highly effective in sup-
pressing audio buzz caused by the 4.5MHz IF beat signal
in Japanese multiplexed (L
R) audio or American (MTS)
Multichannel TV Sound (L
R) signals.
As buzz cancelation is independent of the PLL loop time
constant, other parameters such as automatic phase control
can be optimized to eliminate interference from yback
pulses.
Design Notes
FM Detector Output (Pin 1)
The FM detector output is an emitter follower with a
200
Ω series protection resistor as shown in Figure 5.
In multiplex audio applications where pin 1 is connected
to the input of a multiplexed audio decoder, the input
resistance of the decoder can decrease, causing distortion
of the (L
R) signal. In this case, a 5.1kΩ or larger resis-
tor, R1, should be connected between pin 1 and ground.
Figure 5. FM detector output
In monophonic applications, an RC de-emphasis circuit
should be connected as shown in Figure 6. The time con-
stant is given by R2
× C.
Figure 6. RC de-emphasis circuit
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LA7578 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述: |
| LA7578N | 制造商:SANYO 制造商全稱:Sanyo Semicon Device 功能描述:IF Signal Processing (Super PLL-II VIF + SIF) Circuit for TVs and VCRs |
| LA7583 | 制造商:SANYO 制造商全稱:Sanyo Semicon Device 功能描述:IF Signal Processing Circuit (A2C PLL VIF + SIF) for TVs and VCRs |
| LA7590 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog IC |
| LA7600 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述: |
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