Patent ID: 8829735

Claim:
An input circuit comprising: a signal input; a signal output; a high-pass filter having an input coupled to the signal input and an output, the high pass filter to remove first low frequency components from an input signal presented at the signal input; a summing node coupled to the output of the high-pass filter; a receiver having an input coupled to the summing node and an output coupled to the signal output; and a low frequency restoration feedback unit having an input coupled to the output of the receiver and an output coupled to the summing node, the low frequency restoration feedback unit to provide second low frequency components to the summing node, wherein the second low frequency components track the first low frequency components, wherein the signal input, the input and output of the high-pass filter, the summing node, the input of the receiver, and the output of the low frequency restoration feedback unit all carry differential signals, and wherein the low frequency restoration feedback unit receives a coupling control signal that indicates whether the input circuit should operate in an AC coupling mode or a DC coupling mode, and the second low frequency components are not provided to the summing node in the AC coupling mode.