Patent ID: 6198818
Filing Date: 2001-03-06
Classification: H04L,H04M

Abstract:
An analog front end circuit for use in a data communications equipment (DCE) device, the analog front end circuit connecting the DCE device to a communications line, the analog front end circuit comprising:a transformer comprising a line side and a DCE side;a driver circuit for driving the communications line, the driver circuit having an input terminal coupled to the DCE device for receiving an input from the DCE device, the driver circuit having an output terminal coupled to the DCE side of the transformer for providing an output to the DCE side of the transformer, the output of the driver circuit being inductively coupled via the transformer from the DCE side to the line side of the transformer;a DC blocking capacitor coupled to the line side of the transformer, the DC blocking capacitor and the transformer forming an LC circuit; anda current sensing circuit coupled to the DC blocking capacitor, the current sensing circuit comprising a feedback circuit, the current sensing circuit detecting current passing through a portion of the analog front end circuit and forcing the current passing through said portion of the analog front end circuit to approximately zero wherein the analog front end circuit is provided with a high impedance which prevents an impedance null from existing in frequency bands being used by the DCE device.