Circuit level shifts ac signals: AC
signals can emanate from many sources, and
many of these sources are incompatible with
the most popular interface voltages, such as TTL. A temptation always exists to
capacitively couple the ac signals because
capacitive coupling strips off the dc level.
Capacitive coupling sometimes doesn't work,
because the coupled signal's voltage swings
around ground, so you have to add dc offset
to make.... |