Estudo e Implementação de Filtros Analógicos

Abstract

Analog active frequency filters are electronic circuits that allow the passage of electronic signals in a given frequency range and reject signals from other frequencies. Its use is fundamental in various electronic applications given that the presence of interference and noise in electronic systems is common. The objective of this work was to compare the characteristics of four categories of filters: Butterworth, Chebyshev, Inverse Chebyshev and Bessel based on Sallen-Key topologies and the inverting integrator circuit with DC gain limitation associated with an inverting amplifier. The main electronic device used is the operational amplifier, with which it is possible to perform various mathematical operations such as sum, difference and, mainly for this work, integration using resistors and capacitors according to the topologies used. From the transfer functions of the designed circuits, Bode diagrams were drawn with Scilab and LTspice Softwares in order to analyze the magnitude and phase response in relation to the frequency of the developed filters and then the diagrams of each designed filter were compared. The focus of the implementations were low-pass filters in which all signals with frequencies below a certain frequency are admitted with ideally zero attenuation and all frequencies above this frequency suffer a minimum attenuation that ideally sets the signals to zero. It is observed that the real behavior of a filter does not correspond to the ideal behavior, since there is the presence of a transition band between the pass and rejection bands and there is a compromise between the signal ripple and the transition bandwidth. Each filter has its individual characteristics and based on these characteristics and knowledge of the requirements of each project, it is possible to determine which type of filter best meets the project specifications.