I.L.
MANASWINI - BT15EEE037
J.N.SAI GOWRI - BT15EEE038
AIM :- To study Wide-Band Reject filter
APPARATUS:- 1)op-amps 3 IC741
2)resistors 8 10K
1 3.3K
Rh 15.9k
Rl 20k
3)Capacitors Ch 0.01uF
Cl 0.05Uf
4)Voltage source
CIRCUIT DIAGRAM:-
R1 R2
10kΩ 10kΩ
VEE
-15V
4 U1
2
R5 R7
Ch 6 VEE
3 10kΩ 10kΩ
-15V
4 U3
0.01µF 7 1 5 R6
741
Rh VCC
V1 15.9kΩ15V 10kΩ 2
6
120 Vrms R9
3
10kΩ XBP1
50 Hz R8
VCC 3.3kΩ 7 1 5
0° 741
15V IN OUT
VCC
7 1 5 U2
Rl 15V
3
20kΩ Cl 6
0.05µF
2
4 741
VEE
-15V
R11 R10
10kΩ 10kΩ
THEORY:-
BAND-REJECT FILTERS
The band-reject filter is also called as band-
stop or band-elimination filter. In this filter frequencies are
attenuated in the stop band while they are passed outside this
band. As with band-pass filters band-reject filters can also be
classified as 1) Wide-Band Reject
2) Narrow-Band Reject
Typical Band Stop Filter Configuration
The summing of the high pass and low pass filters means that
their frequency responses do not overlap, unlike the band-pass
filter. This is due to the fact that their start and ending
frequencies are at different frequency points
Generally band-pass filters are constructed by combining a low
pass filter (LPF) in series with a high pass filter (HPF). Band stop
filters are created by combining together the low pass and high
pass filter sections in a “parallel” type configuration as shown.
High pass filter:-
High Pass Filter as its name implies, attenuates low frequencies
and passes high frequency signals. It consists simply of a passive
filter section followed by a non-inverting operational amplifier.
The frequency response of the circuit is the same as that of the
passive filter, except that the amplitude of the signal is
increased by the gain of the amplifier and for a non-inverting
amplifier the value of the pass band voltage gain is given as 1 +
R2/R1.
CIRCUIT DIAGRAM:-
Gain for an Active High Pass Filter
Where:
AF = the Pass band Gain of the filter, ( 1 + R2/R1 )
ƒ = the Frequency of the Input Signal in Hertz, (Hz)
ƒc = the Cut-off Frequency in Hertz, (Hz)
Frequency Response Curve
Low Pass Filter
low pass filter, consists simply of a passive RC filter stage
providing a low frequency path to the input of a non-inverting
operational amplifier.
The frequency response of the circuit will be the same as
that for the passive RC filter, except that the amplitude of the
output is increased by the pass band gain, AF of the amplifier.
For a non-inverting amplifier circuit, the magnitude of the
voltage gain for the filter is given as a function of the feedback
resistor ( R2 ) divided by its corresponding input resistor ( R1 )
value and is given as:
CIRCUIT DIAGRAM
Gain of a low pass filter
Where:
AF = the pass band gain of the filter, (1 + R2/R1)
ƒ = the frequency of the input signal in Hertz, (Hz)
ƒc = the cut-off frequency in Hertz, (Hz)
Frequency Response
v
FREQUENCY RESPONSE CURVE OF WIDE BAND
REJECT FILTER:-
e
Where
fl=High cutoff frequency of lowpass filter.
fl=(1)/(2*pi*Rh*Ch)
fh=Low cutoff frequency of high pass filter.
fh=(1)/(2*pi*Rh*Ch)
fc=Centre frequency of band-reject filter.
√(𝑓𝑙 ∗ 𝑓ℎ)
Band Width=𝑓ℎ − 𝑓𝑐
APPLICATION OF WIDE-BAND REJECT FILTERS -
:
These filters are used as the telephone line noise reducers
and DSL internet services
These are widely used in the electric guitar amplifiers.
These are also used in some of the acoustic applications
like mandolin, base instrument amplifiers
These filters are used to eliminate these unwanted
harmonics
These are used to reduce the static on radio, which are
commonly used in our daily life
CALCULATION:-
fl=(1)/(2*pi*Rl*Cl)=159.15Hz
fh=(1)/(2*pi*Rh*Ch)=1000.19Hz
fc=√(𝑓𝑙 ∗ 𝑓ℎ) =398.97Hz
B.W=𝑓ℎ − 𝑓𝑐=1000.19-159.15=841.05
RESULT:-
The centre frequency of the wide band reject filter Is 398.97Hz
CONCLUSION:-
The circuit deigned reject the frequencies in between 𝑓𝑙
and 𝑓ℎ. The bandwidth of the band stop reject filter depends
on R and C values of the low pass filter circuits and high pass
filter circuit.
