Data Sheet

ADA4075-2

Rev. B | 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.

OUTPUT

DAC OUTN

DAC OUTP

11kΩ

11kΩ

5.62kΩ

1.5kΩ

3.01kΩ

100Ω

5.62kΩ

100kΩ

2.2nF

150pF

270pF

560pF

68pF

47µF

ADA4075-2

1/2

Figure 66. Typical DAC Output Filter Circuit (Differential)