Differential echo cancellation receiver circuitry with dynamic cancellation
of excess DC output current. Differential input circuitry provides for cancellation
of incoming DC voltage and the incoming transmit signal echo while passing the
receive signal. Excess DC current appearing in the input circuitry as part of the
incoming DC voltage and echo signal cancellation is shunted away from the output
circuitry with dynamically biased current shunting circuitry that tracks changes
in the DC current within the input circuitry.