In recent years

several papers have been published on active R notch filters containing only resistors and two operational amplifiers. However

they did not give design concepts for its circuits and the notch attenuation characteristics. Furthermore

the notch attenuation can not be adjusted with these simple filter structures. In this paper

basic thoughts of designing active R filters with two operational amplifiers are first presented. A new active R notch filter with two operational amplifiers and seven resistors is then given. This filter has very low sensitivities to all passive and active parameters

and is suitable for medium-Q high-frequency applications with its notch characteristic being adjustable. At the end of the paper an illustrative example is given. Laboratory experiments have confirmed the theory.It should be pointed out that the circuit presented in this paper may also be used to realize band-pass

low-pass

high-pass or all-pass transfer characteristics at its two different outputs.