Υψηλόβαθμα μονοτελεστικά ενεργά αναλογικά φίλτρα

Abstract

In 1955, Sallen and Key presented a method of designing RC active filters. A catalogue of 2nd- and 1st-order active networks has been given that enabled the designer to achieve thespecified transfer function by cascading the suitable 2nd- and 1st-order building blocks. In 1969, Shepard presented another method of designing RC active filters. A catalogue of 3rd- and 2nd-order active networks, with unity gain (K=1), were given which enabled the designer to achieve the specified transfer function by cascading the suitable 3rd and 2nd-order building blocks. In this Thesis we designed active filters from 2nd- to 8th-order active filters using in each case only one op amp in order to reduce the number of active elements. All resistances will be taken equal to each other, which is attractive from a practical point of view (integration). We have found that a voltage gain larger than unity will decrease the spread of the element values considerably. Further, we found it advantageous to choose two of the capacitances equal to each other (ck+1 = Ck). These choices lead to lower capacitances ratios and it is found that an adjustable voltage gain facilitates, if necessary, a precise adjustment of the filter characteristics. A method was also presented to realize high-pass, band-pass and band-stop functions. Design data table for normalized Butterworth, Chebyshev (0.1, 0.5, 1, 2 and 3 dB ripple) and Bessel filters and example was included for 2nd- to 8th-order filters. Visual feedback of sound is useful as a training aid to help speech impediments such as stuttering and some forms of mental retardation. We divided the audio into many narrow channels using active filters. The energy in each channel is detected and used to control a LED.