Integrated Electronics

FILTERS

Integrated Electronics

Filters

Filters are circuits that are capable ofpassing signals within a band offrequencies while rejecting or blockingsignals of frequencies outside this band.This property of filters is also called“frequency selectivity”

Integrated Electronics

Types of Filters

• Filters are classified into two types

Digital

Analog

Integrated Electronics

Digital FiltersDigital filters: are implemented using a digital computer or special purpose digital hardware

A digital filter is simply the implementation of an equation(s) in computer software.

There are no R, L, C components as such.

However, digital filters can also be built directly into special purpose computers in hardware form.

But the execution is still in software

1-4

Integrated Electronics

Analog Filters

Analog filter are further classified into two types

Active filters

Passive filters

Integrated Electronics

Analog Filters

• Analog filters: may be classified as either passive or active and are usually implemented with R, L, and C components and operational amplifiers

• An active filter is one that, along with R, L, and C components, also contains an energy source

• A passive filter is one that contains only R, L, and C components. It is not necessary that all three be present

Integrated Electronics

Low order Filters

Integrated Electronics

Low pass filters

• Low pass (RC) filters

R

CVI VO

+

_

+

_

Low pass filter circuit

1( ) 1

1( ) 1OV jw jwC

V jw jwRCRi

jwC

Integrated Electronics

Low pass filters

Low pass (RC) filters

0 dB

1

0

1/RC

1/RC

.-3 dB

x0.707

Passes low frequencies

Attenuates high frequencies

Integrated Electronics

High pass filters• High pass (RC) filters

C

RVi VO

+

_

+

_

( )1( ) 1

OV jw jwRCRV jw jwRC

RijwC

High Pass Filter

Integrated Electronics

High pass filters• High pass (RC) filters

0 dB

.

. -3 dB

0

1/RC

1/RC

1/RC

10.707

Bode

Linear

Passes high frequencies

Attenuates low frequencies

x

Integrated Electronics