Hybrid circuit for a broadband modem

A hybrid circuit that couples a broadband modem to a POTS or ISDN telecommunication line (TL) and includes a transformer bridge circuit (TBC) that includes a bridge circuit (BC). The bridge circuit includes four legs formed by impedance matching networks and parts of the transformer, and a differential drive amplifier (DRV) that performs impedance synthesis. A secondary winding (TS) of the transformer is magnetically coupled to the first and the second primary windings and is electrically coupled to the telecommunication line. First and second impedance dividers (Zhin 1 , Zhout 1 and Zhin 2 , Zhout 2 ) are connected to the various nodes to provide outputs to a receive amplifier (RCV). The impedance matching networks (Zm 1 ; Zm 2 ) include various passive and reactive components that together provide an impedance value selected based upon the line impedance reflected into the primary windings (TP 1 ; TP 2 ) of the transformer. To perform the impedance synthesis, the drive amplifier (DRV) is a differential drive amplifier having feedback inputs (FB−, FB+) to which the third (C) and fourth (D) nodes are connected.