Introduction

In the previous chapters, comparatively simple methods have been discussed for the realization of active OA (operational amplifier) RC filters. Many more methods of filter synthesis will be discussed later, providing many more filter circuit configurations. Among this large number of available circuits, the choice of a ‘best’ filter circuit may depend on the specific user's requirements. However, every application ideally requires a practical filter for which performance parameters, like ωo (center frequency or cut-off frequency) and quality (pole-Q), are needed exactly as designed, and expected to remain invariant with use in varying environment. However, in practice, the user is satisfied if the parameters remain within such limits that do not make the filter impractical. Though there are different reasons during fabrication which cause deviations in the performance parameters, there is one factor which is common to all circuits at design stage. This factor can be termed as the first consideration in connection with these deviations. It is studied under sensitivity and is due to the following reasons.

Whatever be the reason for the difference between the practical element value(s) and the original design value(s), performance of the filter gets affected, and it is said that the filter performance parameters are sensitive to the elements used. Sensitivity studies of filter circuit parameters provide the information whether a particular circuit will meet the given specifications under likely tolerances of the elements or not. The studies also help in establishing filter stability and hence the filter's utility in the long term.