Filters: Theory And Practice 1

1 EE 50 July/August 1987 FILTERS: THEORY AND PRACTICE 1 by A.B. Bradshaw The design of filters remains a topic of considerable interest to practitioners in many branches of electronics, in spite of the fact that many of such networks can nowadays be purchased at rela- tively low prices. None the less, there are still many occasions when a filter has to be designed from scratch. This series of articles will look at the theory underlying such design, and in the last part two practical designs will be discussed in detail. As long as there has been elecronic engineering there has been a need for filters: low- pass, high-pass, band-pass, and band-stop. Basically, a filter is an electrical network that will pass signals with frequencies within certain ranges and suppress signals with other frequencies. A network is essentially a number of impedances con- nected together to form a system the behaviour of which depends on the values of the resistances, capacitances, and inductances from w...