Datasheet

Data Sheet ADA4075-2
Rev. C | Page 17 of 24
DAC OUTPUT FILTER
The ultralow voltage noise, low distortion, and high slew rate of
the ADA4075-2 make it an ideal choice for professional audio
signal processing. Figure 66 shows the ADA4075-2 used in a
typical audio DAC output filter configuration. The differential
outputs of the DAC are fed into the ADA4075-2. The ADA4075-2
is configured as a differential Sallen-Key filter. It operates as an
external low-pass filter to remove high frequency noise present
on the output pins of the DAC. It also provides differential-to-
single-ended conversion from the differential outputs of the DAC.
For a DAC output filter, an op amp with reasonable slew rate and
bandwidth is required. The ADA4075-2 has a high slew rate of the
12 V/µs and a relatively wide bandwidth of 6.5 MHz. The cutoff
frequency of the low-pass filter is approximately 167 kHz. In
addition, the 100 kΩ − 47 µF RC network provides ac coupling
to block out the dc components at the output.
07642-054
OUTPUT
DAC OUTN
DAC OUTP
11kΩ
11k
Ω
5.62k
Ω
1.5kΩ
3.01k
Ω
100
Ω
5.62kΩ
100k
Ω
2.2n
F
150pF270p
F560pF
68pF
47
µF
ADA4075-2
1/2
+
Figure 66. Typical DAC Output Filter Circuit (Differential)