There are two good reasons for their wide use in signal conditioning system
design. The first and foremost is the ability of the DA to respond to the difference in
the input signals and to discriminate against noise or interference that may
be common to both inputs. Such a common-mode (CM) input voltage is often a dc
level hum, or other coherent interference, which is desired to be eliminated. Another
reason for using a DA headstage is that it inherently discriminates against changes in the
amplifier’s dc power supply voltages.