Digitally programmable mixed mode universal filter using followers-a minimal realization

Tunable Mixed-Mode Voltage Differencing Buffered Amplifier-Based Universal Filter with Independently High-Q Factor Controllability

“…where (27) illustrates that the order of the filter function is modified due to the parasitic pole ω parasite , (i.e., ω parasite = 1/R w1 C p2 ). However, this effect can be diminished if the proposed circuit is designed to operate at a useful frequency much less than ω parasite or under the following condition: ω << 0.1 ω parasite .…”

“…A deep investigation of the available literature reveals that several exemplary filter topologies introduced in [1,12,16,19,21,26,29,31,32,37,39,43,44] do not provide the different filtering responses in all four modes of operation. In [1][2][3][4][5][6][7][9][10][11][12][13]17,18,20,25,[27][28][29][30]32,36,38,40,41], they require more than two active components for the design. The use of more active components results in higher power dissipation and a large chip area.…”

“…Additionally, a multitude of the previously discussed mixed-mode filters [3][4][5][6][7][8]10,12,16,18,22,23,25,27,31,35,36,38,41,42,44,45] employ an excessive number (at least five) of passive components. It has been observed that the realizations of [3][4][5][6][7][8]12,[14][15][16]18,[21][22][23][24]26,27,31,[33][34][35][37][38][39][41][42][43]45,46] still used some floating passive components, whic...…”

“…It has been observed that the realizations of [3][4][5][6][7][8]12,[14][15][16]18,[21][22][23][24]26,27,31,[33][34][35][37][38][39][41][42][43]45,46] still used some floating passive components, which is unfavorable from integrated circuit (IC) implementation viewpoint. To obtain various filtering responses or to change the operating mode, the designs in [5,7,27,32,42] need structural modification with a programmable switching technique. This technique needs to employ some external switches, which practically lead to increasing switching noise.…”

“…Furthermore, the important filter parameters, i.e., natural angular frequency (ω o ) and quality factor (Q), for the circuits [1,[5][6][7]12,13,[15][16][17]19,20,23,30,33,34,37,38,41] are interactive. Although the circuits of [4,13,22,25,27,[30][31][32]38] allow the realization of different functions of the universal filter with the same topology, they employ two different types of active components, which are not modular, and increase the complexity of the resulting circuit. In other works [8,16,19,24,26,33,39,43,45,46], some mixedmode universal filters based on a single active element were previously reported.…”