New current-feedack operational-amplifier based shadow filters

New voltage-mode electronically tunable notch, bandpass, highpass and lowpass shadow filters are presented. The filters are built around the current-feedback operational-amplifier. In each case one or more of the parameters of the filter can be electronically controlled by adjusting the gain of an external amplifier built around the current-feedback operational-amplifier. Contrary to the current-mode shadow filters where a summing junction must be used, no summing amplifiers are used in these voltage-mode realizations. Experimental results obtained using the AD844 current-feedback operational-amplifier are presented. The results obtained confirm the functionality of the proposed circuits.

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