Filters are used to selectively pass or block ranges of frequencies in electronic circuits. The main types are low-pass filters, which pass low frequencies and block high frequencies; high-pass filters, which do the opposite; band-pass filters, which pass a band of frequencies; and band-stop or band-reject filters, which block a band of frequencies. Filters can be built using passive components like resistors, capacitors, and inductors in configurations like RC, RL, RLC, pi, and T networks or can use active components like op-amps. The document discusses examples and circuit diagrams of each main filter type.

1. LOW PASS FILTER
HIGH PASS FILTER
BAND PASS FILTER
BAND REJECT FILTER

2. • As name suggest it filters come contents of input signal
and give desired output signal.
• In general electrical and electronics engineering
sometimes it is desirable to have circuits capable of
selectively filtering of one frequency or range of
frequencies out of a mix of different frequencies in a
circuit.
• A circuit designed to perform this frequency selection is
called a filter circuit, or simply a filter best example is the
FM or frequency modulation that we use in our daily life

3. • The filter circuits can be made by
two components :-
• 1. PASSIVE
• 2. ACTIVE

4. TYPES OF FILTER☺

5. LOW PASS
FILTER
1

6. • An ideal low-pass filter is a circuit which passes
low-frequency signals and block high-frequency
signals.
• There are three basic kinds of circuits capable of
accomplishing this objective, and many variations of
each one:-
• First-order filter
• Second-order filter
• Higher-order filter
• Active electronic realization

7. CIRCUIT
DIAGRAM

8. CIRCUIT
DIAGRAM
• An RLC circuit is an electrical circuit consisting of a
resistor, an inductor, and a capacitor, connected in
series or in parallel.
• A second-order filter attenuates higher frequencies
more steeply. The Bode plot for this type of filter
resembles that of a first-order filter, except that it falls
off more quickly.
Second order low pass filter(RLC filter)

9. CIRCUIT
DIAGRAM
Higher order passive filters
WE CAN USE MORE CASCADED RC
ALONG WITH SERIES

10. Active low pass filter(with opamp)
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11. PASS2

12. CIRCUIT
DIAGRAM
High pass filters using LC components, i.e. inductors and
capacitors are arranged in ether a pi or T network. As suggested
by its name, the pi network has one series component, and
either side of it there is a component to ground. Similarly the T
network high pass filter has one component to ground and either
side there is a series in line component. In the case of a high
pass filter the series component or components are capacitors
whereas the components to ground are inductors. In this way
these filters pass the high frequency signals, and reject the low
frequency signals. These filters may be used in applications
where there are unwanted signals in a band of frequencies
below the cut-off frequency and it is necessary to pass the
wanted signals in a band above the cut-off frequency of the filter.
HIGH pass filter(RLC filter)

13. Active HIGH pass filter(with op-amp)
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Figure shows an active electronic
implementation of a first-order high-pass filter
using an opamp.
In this case,the filter has a passband gain of -
R2/R1 and has a cutoff frequency of
Because this filter is active, it may have
nonunity passband gain.
That is, high-frequency signals are inverted
and amplified by R2/R1.

14. BANDPASS
3

15. Band pass filter
• A band-pass filter is a device that passes frequencies within
a certain range and rejects (attenuates) frequencies outside
that range.
• These filters can also be created by combining a low-pass
filter with a high-pass filter.
• The bandwidth of the filter is simply the difference between
the upper and lower cutoff frequencies.
• Q factor:-
• A band-pass filter can be characterised by its Q factor. The
Q-factor is the inverse of the fractional bandwidth. A high-Q
filter will have a narrow passband and a low-Q filter will
have a wide passband. These are respectively referred to
as narrow-band and wide-band filters.
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16. Band pass with LC components
• Like the high pass filters and
the low pass filters, there are
two topologies that are used for
these filters, namely the Pi and
the T configurations. Rather
than having a single element in
each leg of the filter as in the
case of the low pass and high
pass filters, the band pass filter
has a resonant circuit in each
leg. These resonant circuits are
either series or parallel tuned
LC circuits.

17. Main terms
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18. Basic RC based band pass filter
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19. Active Band pass filter
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20. Active bandpass filter with stages
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21. BAND STOP
OR
BAND REJECT4

22. Band stop or band rejection filter
• In signal processing, a
band-stop filter or band-
rejection filter is a filter
that passes most
frequencies unaltered, but
attenuates those in a
specific range to very low
levels.
• It is the opposite of a
band-pass filter. A notch
filter is a band-stop filter
with a narrow stop band
(high Q factor).March 29, 2017

23. band stop filter( WITH RC )
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24. Active band stop filter
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These are classified as:
• Wide band reject filters
• Narrow band reject
filters (Notch filters).
Wide band reject filtersNarrow band reject filters (Notch filters).