TUGAS ELENG JUMAT

8/12/2019 TUGAS ELENG JUMAT

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Adam / Ria / Arvin / Ivan / Eufrasia LS-2

Which is more reliable filters using active or passivecomponents ?

Modern active filters are superior in filtering performance, smaller in phsical si!e, andmore "e#i$le in application, compared to traditional passive filters using capacitors, inductorsand/or resistors% &o'ever, the active filters are slightl inferior in cost and operating loss,compared to the passive filters, even at present% Active filters intended for po'er conditioning arealso referred to as (active po'er filters,) (active po'er line conditioners,) (active po'er *ualitconditioners,) (self-commutated S+s static var compensators.,) etc%

he term (po'er conditioning) used in this paper has much $roader meanings than theterm (harmonic filtering%) In other 'ords, the po'er conditioning is not confined to harmonicfiltering, $ut it contains harmonic damping, harmonic isolation, harmonic termination, reactive-po'er control for po'er factor correction and voltage regulation, load $alancing, voltage-"ic0erreduction, and/or their com$inations%

Active filters have three main advantages over passive filters1 Inductors can $e avoided% assive filters 'ithout inductors cannot o$tain a high 3 lo'

damping., $ut 'ith them are often large and e#pensive at lo' fre*uencies., ma havesignificant internal resistance, and ma pic0 up surrounding electromagnetic signals%

he shape of the response, the 3 3ualit factor., and the tuned fre*uenc can often $eset easil $ varing resistors, in some filters one parameter can $e ad4usted 'ithoutaffecting the others% +aria$le inductances for lo' fre*uenc filters are not practical%

he amplifier po'ering the filter can $e used to $uffer the filter from the electroniccomponents it drives or is fed from, variations in 'hich could other'ise significantlaffect the shape of the fre*uenc response%


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What are the advantage/ disadvantage if filters (either low, high and bandpass) use

inductors or capacitor and active components.

Band Pass Filters

he cut-off fre*uenc or 5cpoint in a simple R passive filter can $e accuratel controlled using4ust a single resistor in series 'ith a non-polari!ed capacitor, and depending upon 'hich 'aaround the are connected either a lo' pass or a high pass filter is o$tained%

6ne simple use for these tpes of filters is in audio amplifier applications or circuits such as inloudspea0er crossover filters or pre-amplifier tone controls% Sometimes it is necessar to onlpass a certain range of fre*uencies that do not $egin at 7&!, 8. or end at some high fre*uencpoint $ut are 'ithin a certain fre*uenc $and, either narro' or 'ide%

9 connecting or :cascading: together a single Low Pass Filtercircuit 'ith a High PassFiltercircuit, 'e can produce another tpe of passive R filter that passes a selected range or:$and: of fre*uencies that can $e either narro' or 'ide 'hile attenuating all those outside of thisrange% his ne' tpe of passive filter arrangement produces a fre*uenc selective filter 0no'ncommonl as a Band Pass Filteror BPFfor short%

Band Pass Filter Circuit

;nli0e a low pass filter that onl pass signals of a lo' fre*uenc range or ahigh passfilter'hich pass signals of a higher fre*uenc range, a Band Pass Filterspasses signals 'ithina certain :$and: or :spread: of fre*uencies 'ithout distorting the input signal or introducinge#tra noise% his $and of fre*uencies can $e an 'idth and is commonl 0no'n as thefilters Bandwidth% 9and'idth is defined as the fre*uenc range $et'een t'o specifiedfre*uenc cut-off points 5c., that are


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hen for 'idel spread fre*uencies, 'e can simpl define the term :$and'idth:, 9=as $eingthe difference $et'een the lo'er cut-off fre*uenc 5cL6=ER. and the higher cut-off fre*uenc 5c&I>&ER . points% In other 'ords, 9= ? 5&- 5L% learl for a pass $and filter to functioncorrectl, the cut-off fre*uenc of the lo' pass filter must $e higher than the cut-off fre*uencfor the high pass filter%

he :ideal: Band Pass Filtercan also $e used to isolate or filter out certain fre*uencies that lie'ithin a particular $and of fre*uencies, for e#ample, noise cancellation% 9and pass filters are0no'n generall as second-order filters, t'o-pole. $ecause the have :t'o: reactive component,the capacitors, 'ithin their circuit design% 6ne capacitor in the lo' pass circuit and anothercapacitor in the high pass circuit%

Frequency Response of a 2nd Order Band Pass Filter.

he Bode Plotor fre*uenc response curve a$ove sho's the characteristics of the $and passfilter% &ere the signal is attenuated at lo' fre*uencies 'ith the output increasing at a slope of@27d9/8ecade d9/6ctave. until the fre*uenc reaches the :lo'er cut-off: point 5L% At this


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fre*uenc the output voltage is again B/C2 ? D7%Dof the input signal value or !dB27 log+out/+in.. of the input%

he output continues at ma#imum gain until it reaches the :upper cut-off: point 5&'here theoutput decreases at a rate of -27d9/8ecade d9/6ctave. attenuating an high fre*uenc signals%

he point of ma#imum output gain is generall the geometric mean of the t'o -


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he value of the capacitor 2re*uired to give a cut-off fre*uenc 5&of


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Centre Frequency %quation

=here, 5ris the resonant or centre fre*uenc

5Lis the lo'er -


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capacitor value made $ com$ining together t'o or more individual capacitors is still onecapacitor%

6ur e#ample a$ove sho's the output fre*uenc response curve for an :ideal: $and pass filter'ith constant gain in the pass $and and !ero gain in the stop $ands% In practice the fre*uenc

response of this 9and ass Filter circuit 'ould not $e the same as the input reactance of the highpass circuit 'ould affect the fre*uenc response of the lo' pass circuit components connectedin series or parallel. and vice versa% 6ne 'a of overcoming this 'ould $e to provide some formof electrical isolation $et'een the t'o filter circuits as sho'n $elo'%

Buffering 1ndividual Filter (tages

6ne 'a of com$ining amplification and filtering into the same circuit 'ould $e to use an6perational Amplifier or 6p-amp, and e#amples of these are given in the Operational&-plifiersection% In the ne#t tutorial 'e 'ill loo0 at filter circuits 'hich use an operational

amplifier 'ithin their design to not onl to introduce gain $ut provide isolation $et'een stages%hese tpes of filter arrangements are generall 0no'n as &ctive Filters%
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