參數(shù)資料
型號(hào): LA75691
元件分類: 接收器
英文描述: AM/FM, AUDIO/VIDEO DEMODULATOR, PDIP24
封裝: SDIP-24
文件頁(yè)數(shù): 4/13頁(yè)
文件大?。?/td> 206K
代理商: LA75691
Notes on Sanyo SAW Filters
There are two types of SAW filter that differ in the piezoelectric substrate material used.
Lithium-tantalum (LiTaO3) SAW filters
TSF11s
s s
s ... Japan
TSF12s
s s
s ... US
Although lithium tantalate SAW filters have the low temperature coefficient of -18 ppm/°C, they suffer from a large
insertion loss. However, it is possible, at the cost of increasing the number of external components required, to minimize
this insertion loss by using a matching circuit consisting of coils and other components at the SAW filter output. At the
same time as minimizing insertion loss, this technique also allows the frequency characteristics, level, and other aspects
to be varied, and thus provides increased circuit design flexibility. Also, since the SAW filter reflected wave level is
minimal, the circuit can be designed with a small in-band ripple level.
Lithium niobate (LiNbO3) SAW filter
TSF52s
s s
s ... US
TSF53s
s s
s ... PAL
Although lithium niobate SAW filters have the high temperature coefficient of -72 ppm/°C, they feature an insertion loss
about 10 dB lower than that of lithium tantalate SAW filters. Accordingly, there is no need for a matching circuit at the
SAW filter output. Although the in-band ripple is somewhat larger than with lithium tantalate SAW filters, since they
have a low impedance and a small field slew, they are relatively immune to influences from peripheral circuit
components and the geometry of the printed circuit board pattern. This allows stable out-of-band trap characteristics to be
acquired. Due to the above considerations, lithium tantalate SAW filters are used in applications for the US and Japan
that have a high IF frequency, and lithium niobate SAW filters are used in PAL and US applications that have a low IF
frequency.
Notes on SAW Filter Matching
In SAW filter input circuit matching, rather than matching the IF frequency, flatter video band characteristics can be
acquired by designing the tuning point to be in the vicinity of the audio carrier rather than the chrominance carrier. The
situation shown in figure on the right makes it easier to acquire flat band characteristics than that in figure on the left.
No. 5734-12/13
LA75691
When tuned to the IF frequency
When tuned near S or C
The high-band frequency
response is reduced
SAW filter
characteristics
The high-band frequency response is extended
Frequency
相關(guān)PDF資料
PDF描述
LA75693M AM/FM, AUDIO/VIDEO DEMODULATOR, PDSO24
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