Circuit solutions for a new subclass of fourth-order band-pass filters have been developed, which are implemented on operational amplifiers and have, among other things, paraphase outputs. Basic equations for their transfer function are obtained. In the Micro-Cap environment, computer simulation of the amplitude-frequency characteristics (AFC) was carried out, which shows the possibility of independent adjustment, adjustment of the bandwidth, uneven AFC and center frequency gain.

The circuit design solutions of a new subclass of fourth-order notch filters (NF) are considered, which are implemented on operational amplifiers by sequentially connecting identical second-order links of NF. Equations for their main parameters are given. In the Micro-Cap environment, computer simulation of the amplitude-frequency characteristics was performed, which shows the possibility of independent adjustment of the quality factor of the pole, the frequency of the pole, and the NF transfer coefficient. The proposed circuits differ in the circuitry of the links, as well as in the ways of introducing feedback and options for connecting the input signal source.

A new subclass of Sallen-Key RC-filters with independent adjustment of the main parameters, which are implemented on voltage followers (buffer and operational amplifiers), has been studied. Low- and high-pass filters, band-pass and notch filters are offered, which have the ability to independently adjust the pole frequency, pole quality factor and transmission coefficient with different resistors. Their computer simulation was carried out in the Micro-Cap environment, the amplitude-frequency and phase-frequency characteristics were obtained in the tuning mode using the models of buffer and operational amplifiers built into the Micro-Cap.