<s>
Electronic	B-Architecture
filters	I-Architecture
are	O
a	O
type	O
of	O
signal	O
processing	O
filter	O
in	O
the	O
form	O
of	O
electrical	O
circuits	O
.	O
</s>
<s>
This	O
article	O
covers	O
those	O
filters	O
consisting	O
of	O
lumped	O
electronic	O
components	O
,	O
as	O
opposed	O
to	O
distributed-element	B-Algorithm
filters	I-Algorithm
.	O
</s>
<s>
Electronic	B-Architecture
filters	I-Architecture
remove	O
unwanted	O
frequency	O
components	O
from	O
the	O
applied	O
signal	O
,	O
enhance	O
wanted	O
ones	O
,	O
or	O
both	O
.	O
</s>
<s>
high-pass	O
,	O
low-pass	B-Algorithm
,	O
band-pass	O
,	O
band-stop	O
(	O
band-rejection	O
;	O
notch	O
)	O
,	O
or	O
all-pass	O
.	O
</s>
<s>
The	O
most	O
common	O
types	O
of	O
electronic	B-Architecture
filters	I-Architecture
are	O
linear	O
filters	O
,	O
regardless	O
of	O
other	O
aspects	O
of	O
their	O
design	O
.	O
</s>
<s>
The	O
oldest	O
forms	O
of	O
electronic	B-Architecture
filters	I-Architecture
are	O
passive	O
analog	O
linear	O
filters	O
,	O
constructed	O
using	O
only	O
resistors	O
and	O
capacitors	O
or	O
resistors	O
and	O
inductors	O
.	O
</s>
<s>
These	O
are	O
known	O
as	O
RC	B-Algorithm
and	O
RL	B-Algorithm
single-pole	O
filters	O
respectively	O
.	O
</s>
<s>
Multipole	O
LC	O
filters	O
provide	O
greater	O
control	O
of	O
response	O
form	O
,	O
bandwidth	O
and	O
transition	B-Algorithm
bands	I-Algorithm
.	O
</s>
<s>
These	O
types	O
are	O
collectively	O
known	O
as	O
passive	O
filters	O
,	O
because	O
they	O
do	O
not	O
depend	O
upon	O
an	O
external	O
power	O
supply	O
and	O
they	O
do	O
not	O
contain	O
active	O
components	O
such	O
as	O
transistors	B-Application
.	O
</s>
<s>
A	O
filter	O
in	O
which	O
the	O
signal	O
passes	O
through	O
an	O
inductor	O
,	O
or	O
in	O
which	O
a	O
capacitor	O
provides	O
a	O
path	O
to	O
ground	O
,	O
presents	O
less	O
attenuation	O
to	O
low-frequency	O
signals	O
than	O
high-frequency	O
signals	O
and	O
is	O
therefore	O
a	O
low-pass	B-Algorithm
filter	I-Algorithm
.	O
</s>
<s>
The	O
simplest	O
passive	O
filters	O
,	O
RC	B-Algorithm
and	O
RL	B-Algorithm
filters	I-Algorithm
,	O
include	O
only	O
one	O
reactive	O
element	O
,	O
except	O
for	O
the	O
hybrid	O
LC	O
filter	O
,	O
which	O
is	O
characterized	O
by	O
inductance	O
and	O
capacitance	O
integrated	O
in	O
one	O
element	O
.	O
</s>
<s>
Three-element	O
filters	O
can	O
have	O
a	O
'	O
T	O
 '	O
or	O
'	O
π	O
 '	O
topology	O
and	O
in	O
either	O
geometries	O
,	O
a	O
low-pass	B-Algorithm
,	O
high-pass	O
,	O
band-pass	O
,	O
or	O
band-stop	O
characteristic	O
is	O
possible	O
.	O
</s>
<s>
Likewise	O
,	O
for	O
the	O
illustrated	O
low-pass	B-Algorithm
π	O
filter	O
,	O
the	O
circuit	O
can	O
be	O
connected	O
to	O
a	O
transmission	O
line	O
,	O
transmitting	O
low	O
frequencies	O
and	O
reflecting	O
high	O
frequencies	O
.	O
</s>
<s>
These	O
include	O
digital	O
filters	O
,	O
crystal	B-Algorithm
filters	I-Algorithm
,	O
mechanical	O
filters	O
,	O
surface	O
acoustic	O
wave	O
(	O
SAW	O
)	O
filters	O
,	O
thin-film	O
bulk	O
acoustic	O
resonator	O
(	O
TFBAR	O
,	O
FBAR	O
)	O
based	O
filters	O
,	O
garnet	B-Algorithm
filters	I-Algorithm
,	O
and	O
atomic	O
filters	O
(	O
used	O
in	O
atomic	O
clocks	O
)	O
.	O
</s>
<s>
Electronic	B-Architecture
filters	I-Architecture
can	O
be	O
classified	O
by	O
the	O
technology	O
used	O
to	O
implement	O
them	O
.	O
</s>
<s>
Filters	O
using	O
passive	O
filter	O
and	O
active	O
filter	O
technology	O
can	O
be	O
further	O
classified	O
by	O
the	O
particular	O
electronic	B-Algorithm
filter	I-Algorithm
topology	I-Algorithm
used	O
to	O
implement	O
them	O
.	O
</s>
<s>
Any	O
given	O
filter	O
transfer	O
function	O
may	O
be	O
implemented	O
in	O
any	O
electronic	B-Algorithm
filter	I-Algorithm
topology	I-Algorithm
.	O
</s>
<s>
The	O
filters	O
in	O
this	O
illustration	O
are	O
all	O
fifth-order	O
low-pass	B-Algorithm
filters	I-Algorithm
.	O
</s>
