Electronically controllable bandpass filters with high quality factor and reduced capacitor value: An additional approach

In this paper, a new method is presented to increase the quality factor of bandpass filters employing active elements. Using the proposed method the values of the externally capacitors in filter structure are reduced. In this way chip area which is an important parameter in the integrated circuits can be minimized. Moreover, bandpass filters are investigated from the point of view of stability conditions and effects of the parasitic and non-ideal elements. Considering these effects, operating conditions and boundaries of the bandpass filter are calculated. To validate the feasibility of the method, an application example of bandpass filter used in intermediate frequency (IF) stage of AM receivers is given and the performance of the circuit is demonstrated by comparing the theory and simulation.