Realization of Inverse Active Filters Using Single Current Differencing Buffered Amplifier

Abstract

The authors introduce a new single current differencing buffered amplifier (CDBA) based inverse filter configuration. By appropriate selection of admittances, different inverse filter circuits like inverse high-pass (IHP) circuit, inverse low-pass (ILP) circuit, inverse band-reject (IBR) circuit and inverse band-pass (IBP) circuit can be realized from the same configuration. The capacitors used here are grounded/virtually grounded for all the realizations. The performances of the proposed filters have been judged by using CMOS structure of CDBA with TSMC 0.35 µm technology as well as by using the available IC of current feedback operational amplifier (CFOA) i.e. AD844 based CDBA. The simulation results agreed well with the theoretical results. Monte-Carlo simulation has also been performed to check the robustness of the proposed configuration.

Inverse Analog Filters: History, Progress and Unresolved Issues

“…Thus, theoretically, all these cases represent unstable systems. Now, the fact that a number of authors have come up with first-order inverse all-pass filter [10,19,33], second order IHP [1,9,[11][12][13][14][15][16][17][18]20,22,23,27,28,30,32,35,36,[39][40][41][42][43], IBR [11,12,15,17,22,24,25,27,29,32,35,36] and IAP [8,9,24,27,29] filters, it is a matter of curiosity as to how the observance of instability was not reported by any of them. There could be two possible reasons for this:…”

“…While most of the works described above require two CDBAs, a single-CDBA-based inverse filter structure was proposed in [32] by Paul, Roy and Pal. However, out of the four types of filters realizable (ILP, IBP, IHP, IBR), only the ILP is realizable canonically; all others require three capacitors and, hence, are non-canonic.…”