Continuous Time Active Analog Filters

Realization of fractional order lowpass filter using different approximation techniques

“…These outputs are used in a feed-forward form to get n th order filter with arbitrarily transmission zeros as shown in Figure 3. In this structure, the outputs from the lossless integrators are multiplied by coefficients and then added together to get final output [33], [34].…”

Various-Order Low-Pass Filter with the Electronic Change of Its Approximation

“…Therefore, we usually look for some compromise or a specific characteristic that is most important for us in a given scenario. We can identify typical frequency filters having Butterworth approximation [9][10][11][12][13], filters having Bessel approximation [14][15][16], filters having Elliptic (also called Cauer) approximation [17][18][19], filters having Chebyshev approximation [20][21][22][23] and filters having Inverse Chebyshev approximation [24][25][26]. Considering the steepness of the transition between the pass-band and stop-band area of the magnitude response, Elliptic and Chebyshev approximations are steepest.…”

“…From the proposed research [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], some circuit solutions [12,13,15] present more than one filtering function. However, these functions are typically available from individual circuits (each filter type has its own topology).…”

“…Only the solution in [12] allows the reconfiguration of the type and order of the resulting filtering function (from a single topology) by the implementation of a switching mechanism. Furthermore, as evident from [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], the filters typically follow one particular approximation. This approximation then determines the features of the filter and consequently the applicability of the filter in accordance with the desired requirements of a particular application.…”