The Third Order Active Low-Pass RC-Filters Based on Differential and Differential Difference Operational Amplifiers

A new structure of the third order low-pass RC-filter (ARCF-III) designed for practical use as a spectrum limiter at the input of various analog-to-digital converters of the A/D Interface of the instrumentation and control system is considered. It is shown that in the proposed ARCF-III the high guaranteed attenuation of the amplitude-frequency characteristic is provided outside the operating band. Three modifications of ARCF-III are developed for its implementation based on differential and differential difference operational amplifiers. Analytical expressions defining the conditions for the synthesis of ARCF-III are presented. The results of computer simulation of the amplitude-frequency characteristic are discussed.