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US 3,955,150 AGranted
Active-R filter
AssigneeThe United States of America as represented by the United States Energy Research and Development Administration
InventorMichael A. Soderstrand
Life of this patent
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Abstract
An operational amplifier-type active filter in which the only capacitor in the circuit is the compensating capacitance of the operational amplifiers, the various feedback and coupling elements being essentially solely resistive.
Claims6
An active-R filter consisting essentially of first and second operational amplifiers, each amplifier including an inverting input, a noninverting input and an output;
- means for directly connecting an input resistor through a first junction to the inverting input of said first operational amplifier;
- means for directly connecting the output of said first operational amplifier through a second junction to the noninverting inpput of said second operational amplifier;
- means for directly connecting a first feedback resistor between the inverting input of said first operational amplifier through a third junction to the output of said second operational amplifier;
- means for directly connecting a second feedback resistor between the inverting input and the output of said first operational amplifier from said first junction to said second junction;
- and means for connecting the noninverting input of said first operational amplifier and the inverting input of said second operational amplifier to ground, said first junction of said input, first feedback and second feedback resistors and the inverting input of said first operational amplifier being a high-pass filter output, said second junction of said second feedback resistor and the output of said first operational amplifier and the noninverting input of said second operational amplifier being a band-pass filter output, and said third junction of said first feedback resistor and the output of said second operational amplifier being a low-pass filter output.
2 more elements
Dependencies are inferred from the claim text.