Patent ID: 6642779
Filing Date: 2003-11-04
Classification: H03H,H03J

Abstract:
A filter, having a positive input, a negative input, a positive output and a negative output, for processing an input signal comprising:a first operational amplifier (OPAMP) having a first positive OPAMP input, a first negative OPAMP input, a first positive OPAMP output and a first negative OPAMP output, wherein the first positive OPAMP output provides a first positive voltage supply and the first negative OPAMP output provides a first negative voltage supply; a positive input circuit portion, wherein the positive input circuit portion comprises, a first resistor coupled to the positive input of the filter, a second resistor coupled in series to the first resistor to form a node between the first and second resistors, a third resistor coupled to the node between the first and second resistors, and a first capacitor coupled between the first positive voltage supply and the second resistor; a negative input circuit portion, wherein the negative input circuit portion comprises, a fourth resistor coupled to the negative input of the filter, a fifth resistor coupled in series to the fourth resistor to form a node between the fourth and fifth resistors, a sixth resistor coupled to the node between the fourth and fifth resistors, wherein the sixth resistor couples to the third resistor, and a second capacitor coupled between the first negative voltage supply and the fifth resistor; a third capacitor and a fourth capacitor coupled in parallel between the second and fifth resistors; a seventh resistors coupled between the second resistor and the first positive OPAMP input; an eighth resistor coupled between the fifth resistor and the first negative OPAMP input; a fifth capacitor coupled between the first negative OPAMP output and the first positive OPAMP input to provide feedback; a first T-network having a ninth resistor, a tenth resistor, and an eleventh resistor, wherein the ninth resistor and the tenth resistor are connected in series between two nodes that are connected to a non-fixed voltage level between the first negative voltage supply and the second resistor, the ninth and tenth resistors coupled to form a first junction, the eleventh resistor coupled between the first junction and a voltage supply source; a twelfth resistor coupled between the voltage supply source and the tenth resistor; a sixth capacitor coupled between the first positive OPAMP output and the first negative OPAMP input to provide feedback; a second T-network having a thirteenth resistor, a fourteenth resistor, and a fifteenth resistor, wherein the thirteenth resistor and the fourteenth resistor are connected in series between two nodes that are connected to a non-fixed voltage level between the first positive voltage supply and the fifth resistor, the thirteenth and fourteenth resistors coupled to form a second junction, the fifteenth resistor coupled between the second junction and the voltage supply source; a sixteenth resistor coupled between the voltage supply source and the fourteenth resistor; a second OPAMP, having a second positive OPAMP input, a second negative OPAMP input, a second positive OPAMP output and a second negative OPAMP output, wherein the second positive OPAMP output provides a second positive voltage supply and the second negative OPAMP output provides a second negative voltage supply; an intermediate positive input circuit portion coupled between the first and second OPAMPS, wherein the intermediate positive input circuit portion comprises, a seventeenth resistor coupled between the first negative OPAMP output and the second positive OPAMP input, an eighteenth resistor coupled to the first negative OPAMP output, a nineteenth resistor coupled to the eighteenth resistor, and a seventh capacitor coupled between the eighteenth resistor and the second positive OPAMP input; an intermediate negative input circuit portion coupled between the first and second OPAMPS, wherein the intermediate negative input circuit portion comprises, a twentieth resistor coupled between the first positive OPAMP output and the second negative OPAMP input, a twenty-first resistor coupled to the first positive OPAMP output, a twenty-second resistor coupled between the twenty-first and nineteenth resistor, and an eighth capacitor coupled between the twenty-first resistor and the second negative OPAMP input; a first feedback portion coupled between the second negative OPAMP output and the second positive OPAMP input, wherein the first feedback portion comprises, a third T-network having a twenty-third resistor, a twenty-fourth resistor, and a twenty-fifth resistor, wherein the twenty-third resistor and the twenty-fourth resistor coupled to form a third junction, the twenty-fifth resistor coupled between the third junction and the voltage supply source, a twenty-sixth resistor coupled between the voltage supply source and the twenty-fourth resistor, a ninth capacitor coupled between the first positive power supply and the twenty-sixth resistor, and a twenty-seventh resistor coupled between the twenty-sixth resistor and the second positive OPAMP input; a second feedback portion coupled between the second positive OPAMP output and the second negative OPAMP input, wherein the second feedback portion comprises, a fourth T-network having a twenty-eighth resistor, a twenty-ninth resistor, and a thirtieth resistor, wherein the twenty-eighth resistor and the twenty-ninth resistor coupled to form a fourth junction, the thirtieth resistor coupled between the third junction and the voltage supply source, a thirty-first resistor coupled between the voltage supply source and the twenty-ninth resistor, a tenth capacitor coupled between the first negative power supply and the thirty-first resistor, and a thirty-second resistor coupled between the twenty-ninth resistor and the second negative OPAMP input; and an output circuit portion coupled to the second OPAMP, wherein the output circuit portion comprises, a thirty-third resistor coupled to the second negative OPAMP output, a eleventh capacitor coupled between the thirty-third resistor and the second positive OPAMP input to provide feedback, a thirty-fourth resistor coupled in series to the thirty-third resistor, a thirty-fifth coupled in series to the thirty-fourth resistor, a thirty-sixth resistor coupled between the thirty-fifth resistor and the second positive OPAMP output, and a twelfth capacitor coupled between the thirty-sixth resistor and the second negative OPAMP input to provide feedback.