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US 7,123,083 B2Granted
Active filter circuit with operational amplifier
OwnerNorbert Greitschus, Stefan Noeinventors
Life of this patent
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Abstract
An at least second-order active filter circuit includes an operational amplifier (Op) whose frequency response, in conjunction with an RC network (R1, R2, C1, C2), serves to set a predetermined low-pass characteristic. The frequency response of the operational amplifier (Op) forms an integral part of this low-pass characteristic.
Claims2
An active filter circuit, comprising:
- an operational amplifier (Op) that includes a transconductance amplifier having a transconductance (gm) controlled by a bias circuit to be inversely proportional to a transconductance determining resistor Rb value within said bias circuit, wherein said operational amplifier (OP) has a low-pass frequency response controlled by said transconductance (gm) and has a transit frequency (fT) less than approximately 60 MHz.
An active filter circuit, comprising:
- an operational amplifier (Op) that includes a transconductance amplifier having a transconductance (gm) controlled by a bias circuit to be inversely proportional to a transconductance determining resistor Rb value within said bias circuit, wherein said operational amplifier (OP) has a low-pass frequency response controlled by said transconductance (gm) and has a transit frequency (fT) less than ten times greater than a cut-off frequency ωg for the active filter circuit.
Dependencies are inferred from the claim text.