A synthesis of high‐order active R filter

Abstract Active R filters consisting of resistors and finite‐GB‐product operational amplifiers have been reported in the literature. Most of them are of second order. Filter functions of higher order can be realized by second‐order blocks connected in cascade. A second‐order highpass filter or a filter with poles can not be cascaded if it is realized with two operational amplifiers since the filter output is not the amplifier output. This paper proposes a new active R filter which realizes an nth order filter function with n operational amplifiers. Lowpass, bandpass, and highpass filters with or without poles can be realized by selecting input and grounded terminals. The proposed method is featured with simple circuitry and ease of design. A fifth‐order lowpass filter will be shown to have theoretical and measured characteristics which are in good agreement.