When are differential pairs needed?
There are three reasons to use differential pairs in a digital or analog signal path. Where the ground connections between the ends of the signal path are poor. The most important one is that the ground connection between the two ends of the signal path can be very poor and data quality will not be compromised.Compare this to a single-ended signal path such as LVCMOS, where the signal arriving at the receiver is compared to a reference level in the receiver. If the grounds between the two ends are offset, the logic levels will be offset and one or the other of the two logic levels is compromised. This ability to “ignore” ground offsets has been the backbone of the wired Internet from the onset. In the case of Ethernet,the two ends of these links are transformer coupled. Where there is significant attenuation along the signal path. A second reason to use differential signaling is that the link can suffer substantial attenuation of the signal and still function prop