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Worapong TANGSRIRAT Wanlop SURAKAMPONTORN Nobuo FUJII
In this paper, is shown an approach to realize leapfrog structures obtained from proto-type passive RLC ladder filters using current differencing buffered amplifiers (CDBA) as active elements. The use of the CDBA's provides advantages that the realization procedure is simplified and the number of active components required is reduced. The approach is quite suitable for the realization of band-pass ladder filters, which generally requires a complicated structure to simulate LC series and/or parallel resonant branches by the conventional opamp-based leapfrog filters. A simple circuit configuration of the CDBA suitable for high frequency and low power supply voltage applications is also presented. As design examples, a fifth-order Butterworth lowpass ladder filter and a sixth-order Chebyshev bandpass ladder filter are designed. The effectiveness and the correctness of the proposed approach and the characteristics of the proposed filters are verified and examined through computer simulation.
A new single resistance controlled quadrature oscillator using two current differencing buffered amplifiers (CDBAs), four resistors and two grounded capacitors is presented. Outputs of two sinusoidal signals with 90phase difference are available in the proposed quadrature oscillator. The oscillation condition and oscillation frequency of the proposed quadrature oscillator are independently controllable through different resistors. The proposed quadrature oscillator employs only grounded capacitors. The use of only grounded capacitors is ideal for integration. Simulation results are included.