AD8476 - Driving signals across a cable

Document created by analog-archivist Employee on Feb 23, 2016
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I want to drive a cable differentially. Can I use AD8476 for driving signals
across a cable?


Yes, but there are some limitations.
Cables present complex impedance loading at the output of  the amplifier. In
order to drive a cable, AD8476 requires a resistor in series with each output,
and the value depends mostly on the cable capacitance. A 100-Ohm resistor on
each output is a good place to start, but it requires some experimentation to
verify that the amplifier has sufficient phase margin. A good way to verify
this is by looking at the step response of the amplifier and making sure there
is no excessive ringing at the output terminals. It is also good practice to
add provisions for an additional load at the output and an RC snubber (an R and
a C in series load between the output terminals). In a noisy environment, best
results can be achieved using a shielded twisted pair, rather than coax or
triax, which are not balanced. Unshielded twisted pair may be okay too,
depending on the amount of noise present. Chip ferrites may be necessary on the
receiver side. Keep in mind that maintaining good balance and matching between
the two lines is critical in rejecting the noise.