Reducing Nonideal Op-Amp Effects in Active Filters by Minimizing the Gain-Sensitivity Product (GSP)

It is shown that the effects of finite amplifier gain and gain-bandwidth product and of the variations of these quantities, on the transfer characteristics of an active filter can be expressed in terms of the gain-sensitivity product (GSP). To minimize these effects, it is sufficient, in most practical cases; to minimize the GSP with respect to, the pole Q. Among other things, the expressions obtained also demonstrate the influence of the op-amp frequency compensation on the poles of an active filter. Experimental results comparing the pole variation of active filters With and without minimized GSP, coincide accurately with the theoretical results obtained in the paper. It is shown that considerable improvement in pole and transfer-characteristic stability of active filters can be expected by minimizing the GSP.