Second-Order Filters with Independent Setting and Adjustment of Basic Parameters
Keywords:active filter, second-order filter, pole frequency, Q factor
A new topology of the second-order low-pass filter containing three operational amplifiers is proposed. As known, a feature of second-order filters based on operational amplifiers is the interdependence of the main filter parameters, such as the pole frequency, Q factor and gain. The second-order filters synthesized by the state variable method have the smallest relationship between the main parameters, but they also do not allow independent adjustment of the gain and Q factor, and contain at least three operational amplifiers.
The proposed low-pass filter topology also contains three operational amplifiers and provides the possibility of independent setting of the pole frequency, Q factor and gain, as well as the possibility of independently adjustment of the Q factor and gain. Relationships have been obtained that relate the pole frequency, Q factor and filter gain to the nominal values of the passive filter elements. On the basis of these ratios, the possibility of independently changing the Q factor and gain of the filter is shown.
On the basis of this topology, a second-order universal filter was synthesized with the possibility of independent setting and adjustment of the main parameters. A cut-off filter with independent installation and adjustment of the main parameters is also offered.
Examples of second-order low-pass filter calculations and simulation results are given, which confirm the correctness of the calculations. Also, the results of modeling universal and rejection filters are given.
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Copyright (c) 2023 Ілля Кирпатенко, Руслан Антипенко, Андрій Мовчанюк, Володимир Фесіч
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