New Bandpass Shadow Filters with Multi Feedback-Amplifiers

This paper presents new electronically tunable bandpass filters. The electronic tuning of the center frequency of each filter can be achieved by adjusting the gain of one or more of the voltage-amplifiers connected in the feedback path of the proposed topology without disturbing the constituents of the filter itself; this results in a shadow filter. Experimental results obtained using the AD741 operational amplifier and the AD844 current-feedback operational amplifier are included.