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WM8774
RECOMMENDED EXTERNAL COMPONENTS
It is recommended that a lowpass filter be applied to the output from each DAC channel for Hi Fi
applications. Typically a second order filter is suitable and provides sufficient attenuation of high
frequency components (the unique low order, high bit count multi-bit sigma delta DAC structure used
in WM8774 produces much less high frequency output noise than competitors devices). This filter is
typically also used to provide the 2x gain needed to provide the standard 2Vrms output level from
most consumer equipment. Figure 34 shows a suitable post DAC filter circuit, with 2x gain.
Alternative inverting filter architectures might also be used with as good results.
4.7kΩ
4.7k
Ω
+VS
_
51
Ω
10uF
1.8k
Ω
7.5KΩ
+
+
-VS
1.0nF
680pF
47k
Ω
Figure 34 Recommended Post DAC Filter Circuit
PP Rev 1.0 June 2002
39
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
