Active-RC Filters Suitable as Antialiasing and/or Reconstruction Filters

The discrete time signal processing circuit requires an anti-aliasing filter at the input and a reconstruction filter at the output, generally. In this paper, selected basic structures of biquads are described and compared with a view to the degradation of the attenuation over the transient frequency of the operational amplifier. Concretely, low-pass and bandpass Sallen-Key, Huelsman (i.e. multi feedback) and non-cascade filter structures are confronted with the limits of a real operational amplifier. Firstly, the reasons for the degradation of the attenuation are explained theoretically. Secondly, these conclusions are verified by simulations. These simulations were performed by spice-like circuit simulator MicroCap version 11.