Active RC and RLC Rejection Filters of the Sallen-Key Class Based on Voltage Followers

To suppress interference in the communication lines of measuring and medical system sensors most modern rejection filters (RF) use active adders based on the operational amplifiers (OA). This imposes restrictions on the applied element base and RF frequency range. The analysis of the existing rejection ARC filters of the Sallen-Key family revealed the disadvantages of filters implemented only on non-inverting voltage repeaters. The article suggests new architectures of the active RC and RLC filters of the Sallen-Key class based on the voltage followers, which have the property to adjust independently the main parameters by different resistors. The mathematical analysis of the transfer functions of the RF given in this article shows several ways to independently adjust the bandwidth of the barrier of the rejection ARC filter. The results of computer modeling of RF circuits and their some modifications are presented.