The Versatile All-pass Filter

Abstract

It is shown that two other types of filters, viz., band-pass and band-reject, can be derived from a given all-pass filter. For illustration, we consider RC active all-pass filters, and show how starting from such a given circuit, one can obain band-pass or band-reject filters, simply by subtraction from, or addition to, unity, to the all-pass one. The corresponding circuit diagrams for implementations are also shown, and simulation plots have been drawn to illustrate the validity of the above facts.