Patent ID: 7733165

Claim:
A circuit arrangement with interference protection, comprising: a power supply terminal configured to receive an external power supply signal from an external power supply line; an internal supply line and a ground line; a first circuit connected to the power supply terminal and to the ground line and configured to provide an internal supply signal on the internal supply line, said internal supply signal derived from the power supply signal; a second circuit connected to the internal supply line and to the ground line and configured to be supplied by the internal supply signal; and a protective circuit connected to the external power supply line and to the ground line and configured to be supplied by the power supply signal, the protective circuit further coupled to the internal supply line and configured to suppress interfering signals caused by the second circuit on at least one of the internal supply line and the ground line from interfering with the first circuit and vice versa, wherein the protective circuit comprises an element comprising an admittance characteristic in a first frequency range, and a transformation circuit coupled to the element and configured to transform said the admittance characteristic in at least a second frequency range, wherein the first circuit and the protective circuit are selectable in response to an activation signal.