Integrated circuit having on die structure providing capacitance in amplifier feedback path

Abstract

An amplifier structure includes shield conductors that are provided spatially adjacent to elongated feedback signal lines that couple a feedback circuit to an amplifier input. The shield conductors are provided between the feedback signal lines and a ground plane, which interrupts a parasitic capacitance that otherwise would be established between the feedback signal line and ground. The shield conductors are electrically coupled to the amplifier's outputs which create a capacitance between the output terminal and the feedback signal line. In some embodiments, the capacitance generated between the output terminal and the feedback signal line can suffice as a capacitor in a feedback path of the amplifier and be contained in an integrated circuit die on which the amplifier is manufactured. Optionally, a structure may be provided that eliminates common mode signals on the feedback lines while simultaneously preserving the common mode signals on the amplifier output terminals. In this option, a second amplifier is provided that, in response to common mode variations at the output terminal, generates counterbalancing voltage variations on a second circuit that is coupled to the feedback lines at their source. The two variations cancel each other out at nodes from which the feedback lines originate, which substantially reduces feedback common mode variation even when there is common mode variation at the output terminals.