Patent ID: 7957522

Claim:
A programmable telephone line impedance matching circuit for coupling to a telephone line through an operational transconductance amplifier, the matching circuit having AC feedback from the telephone line, comprising an integrated circuit having: analog circuitry coupled between a matching circuit input and a matching circuit output, the analog circuitry providing time continuous amplification between the matching circuit input and the matching circuit output; the time continuous amplification having a programmable feedback resistance programmable to cause an output impedance at the operational transconductance amplifier output to match a plain series resistance of any of a plurality of characteristic telephone line impedances; a feedback amplifier having a capacitance in its feedback circuit, an output of the analog circuitry being coupled through a first switched capacitor circuit to an input of the feedback amplifier, a second switched capacitor circuit being coupled in parallel with the capacitance in the feedback circuit, an output of the feedback amplifier being coupleable to an input of the analog circuitry, the switched capacitor circuits synthesizing resistances; and feedback capacitance coupled in parallel with the programmable feedback resistance to provide anti-aliasing filtering for an input signal and smoothing filtering from the switched capacitor circuits.