Patent ID: 6973182

Claim:
An apparatus including differential echo cancellation receiver circuitry with dynamic cancellation of excess DC output current, comprising: resistive input circuitry that responds to reception of a DC power voltage, a differential input signal, a common mode DC current and a differential replica signal current by providing a first intermediate differential signal, wherein said differential input signal includes a DC input signal component corresponding to said DC power voltage, a transmit signal component and a receive signal component, said differential replica signal current corresponds and is opposite in polarity to said transmit signal component, and said first intermediate differential signal includes a first differential signal current corresponding to said receive signal component and substantially zero transmit signal component, and first and second differential DC current phases, current control circuitry, coupled to said resistive input circuitry, that responds to reception of a DC reference voltage, a replica bias signal and said first intermediate differential signal by providing a second intermediate differential signal including a second differential signal current corresponding to said first differential signal current, and first and second shunt DC currents; differential amplifier circuitry, coupled to said current control circuitry and including differential negative feedback circuitry coupled between first and second differential input terminals and first and second differential output terminals, that responds to reception of said second intermediate differential signal via said first and second differential input terminals by providing a corresponding differential output signal via said first and second differential output terminals; and bias signal generator circuitry, coupled to said current control circuitry, that responds to reception of said DC power voltage, said DC reference voltage, and a replica DC current substantially equal to said common mode DC current by providing said replica bias signal, wherein said replica bias signal tracks changes in said first and second differential DC current phases such that said first and second shunt DC currents are substantially equal to said first and second differential DC current phases, respectively.