Patent ID: 6741120
Filing Date: 2004-05-25
Classification: H03H

Abstract:
An active filter comprising:a summing amplifier having an input and an output, wherein the output of the summing amplifier provides the output of the filter; a first RC integrator having an input and an output and configured to emulate a first capacitance, wherein the output of the first RC integrator is coupled to the input of the summing amplifier; a second RC integrator having an input and an output and configured to emulate a second capacitance; a third RC integrator having an input and an output and configured to emulate a third capacitance, wherein the output of the third RC integrator is coupled to the input of the summing amplifier; a fourth RC integrator having an input and an output and configured to emulate an inductance, wherein the input of the fourth RC integrator is coupled to the outputs of the first and second RC integrators and the output of the fourth RC integrator is coupled to the inputs of the first and second RC integrators; and a selectable input stage having a first state and a second state, wherein in the first state the input stage is configured to provide a DC-coupled non-capacitive input to at least one RC integrator and in the second state the input stage is configured to provide an AC-coupled capacitive input to at least two RC integrators.