A high‐frequency active RC filter based on pole sensitivity to the GB product

Abstract

If a general purpose operational amplifier is treated as an ideal model in constructing an active RC filter, the filter performance begins to degrade at several kHz, depending on the frequency realized and Q. The main cause is the finite GB product; the second order poles, the output resistance and the input capacitance may be secondary factors. In this paper, a previously reported filter, using a non-inverting amplifier and compensating only for the GB product, is treated. A design method is proposed to reduce the pole sensitivity to the GB product in addition to compensating for the effects due to imperfection of the second order poles, output resistance, and input capacitance. Concerning the design sequence, a design method is first shown that reduces the pole sensitivity to the GB product. The two types of circuit parameters are adjusted so that the amplitude errors due to the above imperfections are minimized. By means of the present method, the degradation of filter characteristics due to these imperfections can be prevented to a great extent. This is shown by configuration examples and experimental examples. © 1998 Scripta Technica, Electron Comm Jpn Pt 3, 82(1): 30–40, 1999