Cirrus-logic AN241 User Manual download pdf (Page 5)

AN241

Figure 3. Single-Ended to Differential Input Buffer

3.4 Overview of the Filter Topology

3.4.1 High Pass Filter and DC Biasing

The first stage of the buffer forms a high pass filter and provides the proper biasing to the positive termi-

nals of the op-amps. The value of the resistors denoted as “R” will vary depending on the optimal DC bias

for the given converter. Typically this is around half of the VA voltage supply. The high pass filter is formed

from the combination of the AC-coupling capacitor along with the resistor that connects the positive ter-

minal of the op-amp to the DC bias voltage. The 3dB corner of the high pass filter can be calculated as

follows:

Ω

µ µ

Ω

µµ

Ω

µ µ

Ω

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Cirrus-logic AN241 User Manual Page 5