DE LA SALLE UNIVERSITY DASMARINASCOLLEGE OF ENGINEERING, ARCHITECTURE AND TECHNOLOGY

Assignment:Research on Electronic Filters

SCORE:

What is an Electronic Filter?

analog circuitswhich performsignal processingfunctions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones, or both. Electronicfilterscan be: passiveoractive analogordigital high-pass,low-pass,band-pass,band-stop(band-rejection; notch), orall-pass. discrete-time(sampled) orcontinuous-time linearornon-linear infinite impulse response(IIR type) orfinite impulse response(FIR type)The most common types of electronic filters arelinear filters, regardless of other aspects of their design. See the article on linear filters for details on their design and analysis.

The oldest forms of electronic filters are passive analog linear filters, constructed using onlyresistorsandcapacitorsor resistors andinductors. These are known as RC and RL single-polefilters respectively. More complex multipole LC filters have also existed for many years, and their operation is well understood.

Hybrid filters are also possible, typically involving a combination of analog amplifiers withmechanical resonatorsor delay lines. Other devices such asCCDdelay lineshave also been used as discrete-time filters. With the availability of digital signal processing, active digital filters have become common.

Passive filters

Passive implementations of linear filters are based on combinations ofresistors(R),inductors(L) andcapacitors(C). These types are collectively known aspassive filters, because they do not depend upon an external power supply and/or they do not contain active components such as transistors.

Single element types

A low-pass electronic filter realised by anRC circuitThe simplest passive filters,RCandRLfilters, include only one reactive element, excepthybrid LC filterwhich is characterized by inductance and capacitance integratein one element.

L filterAn L filter consists of two reactive elements, one in series and one in parallel.

Multiple element types Multiple element filters are usually constructed as aladder network. These can be seen as a continuation of the L,T and designs of filters. More elements are needed when it is desired to improve some parameter of the filter such as stop-band rejection or slope of transition from pass-band to stop-band.

Active filtersActive filtersare implemented using a combination of passive and active (amplifying) components, and require an outside power source.Operational amplifiersare frequently used in active filter designs. These can have highQ factor, and can achieveresonancewithout the use of inductors. However, their upper frequency limit is limited by the bandwidth of the amplifiers.