On realizing system functions with independently controlled poles and zeros using standard operational amplifiers

A recent letter by Steber and Krueger reports that any system function of order n may be simulated using at most (n+4) operational amplifiers. The present letter shows that all such systems can in fact be realized using only (n+3) operational amplifiers. More significantly, this letter contradicts the validity of another result by Seely by pointing out that even if all the poles of T(s) are simple and distinct it may not always be possible to realize it using only (n+1) operational amplifiers.