Unwanted portions of a signal, such as a DC pedestal, can be
difficult to reject in a single supply circuit. A DC pedestal
voltage most typically appears at the output of an operational
amplifier with a small signal riding on top of it. This
pedestal voltage is required in the analog domain to insure
that the small signal that contains the pertinent information
never falls below the ground potential, where clipping will
occur. In order to digitize this type of signal, the DC offset
forces the designer to use extremely high resolution (20 plus
bits), wide dynamic range A/D converters to capture the
small signal that is of interest to a reasonable resolution such
as 12 bits. The DS converters, ADS1210, ADS1211,
ADS1212, or ADS1213, are appropriate for this function.
An alternative to using a high resolution converter would be
to add an analog stage where the signal is level shifted to
eliminate the DC offset. Unfortunately, this may complicate
matters further in creating a situation where dual supplies
are required.