These types are collectively known as passive filters, because they do not depend upon an external power supply and they do not contain active components such as transistors. Passive implementations of linear filters are based on combinations of resistors (R), inductors (L) and capacitors (C). Cauer's theory allowed filters to be constructed that precisely followed some prescribed frequency function.Ĭlassification by technology Passive filters A major step forward was taken by Wilhelm Cauer who founded the field of network synthesis around the time of World War II. Together with improved filters by Otto Zobel and others, these filters are known as image parameter filters. Campbell's filter was a ladder network based on transmission line theory. The first of these filters was the constant k filter, invented by George Campbell in 1910. Multipole LC filters provide greater control of response form, bandwidth and transition bands. However, these simple filters have very limited uses. These are known as RC and RL single- pole filters respectively. The oldest forms of electronic filters are passive analog linear filters, constructed using only resistors and capacitors or resistors and inductors. See the article on linear filters for details on their design and analysis.

The most common types of electronic filters are linear filters, regardless of other aspects of their design.

infinite impulse response (IIR type) or finite impulse response (FIR type).

discrete-time (sampled) or continuous-time.

high-pass, low-pass, band-pass, band-stop (band-rejection notch), or all-pass.

These components can be in discrete packages or part of an integrated circuit.Įlectronic filters remove unwanted frequency components from the applied signal, enhance wanted ones, or both. That is, using components and interconnections that, in analysis, can be considered to exist at a single point. This article covers those filters consisting of lumped electronic components, as opposed to distributed-element filters. The antenna is connected to the screw terminals to the left of center.Įlectronic filters are a type of signal processing filter in the form of electrical circuits. Television signal splitter consisting of a high-pass filter (left) and a low-pass filter (right). ( March 2013) ( Learn how and when to remove this template message) Please help to improve this article by introducing more precise citations. This article includes a list of general references, but it lacks sufficient corresponding inline citations.

T and pi filter design