8.2.2.1 Interfacing the OPA521 to the AC Mains

The line coupling circuit is one of the most critical segments of a power-line modem. The line coupling circuit has two primary functions: first, to prevent the high voltage, low frequency of the mains (commonly 50 Hz or 60 Hz) from damaging the low-voltage modem circuitry; and second, as the name implies, to couple the modem signal to and from the ac mains.