Why Low Pass Filter is not working ?

Thread Starter

Umeshngr

Joined Dec 26, 2016
4
I have made this low pass filter with help for Texas Instrument pdf .I have made this on Circuit Simulator ' Proteus'.I kept cut-off about 330 Hz.Sin wave generator is in input .
When I kept frequency above 350 Hz still it is giving me a beep..
I cant understand what kind of thing is happening.?
I am beginner.
I used LM741 OP-AMP .Capacitor I used .1uF(down) and .2 uF(up).And see below for more informations.Capture.JPG
 

bertus

Joined Apr 5, 2008
20,240
Hello,

@shteii01 , R5 and R6 will provide a virtual ground for the LM741.
(they will put the + input at 1/2 the supply).
The supply voltage must be higher as 10 Volts to work.
The circuit will work, but R5 and R6 will also influence the cutoff.
The LM741 will NOT have the power to drive a speaker.

Bertus
 

Thread Starter

Umeshngr

Joined Dec 26, 2016
4
lm741 is dual supply. you are using one supply.
I also worked on duel supply.With help of "Texas Instrument pdf".Then showed me with both one supply low pass filter and dual supply low pass filter.I kept this one last, at last both of them is not working.
 

bertus

Joined Apr 5, 2008
20,240
Hello,

As said, the LM741 can not drive the speaker.
replace the speaker with a 10K resistor and test again.

Bertus
 

Thread Starter

Umeshngr

Joined Dec 26, 2016
4
Hello,

As said, the LM741 can not drive the speaker.
replace the speaker with a 10K resistor and test again.

Bertus
I did as you said,graph is like this what ever frequency I choose in input.Above 350 Hz,gain is decreasing and gain at 2K Hz completely become zero.Frequency above 350 Hz not filtered abruptly...It is slowly filtering...Then what should I do for complete removal above 350Hz.Thanks for your reply.
Capture.JPG
 

crutschow

Joined Mar 14, 2008
24,129
A second-order low-pass filter rolls off at 12dB/octave (40dB/decade) above the corner frequency.
The higher the filter order, the faster it rolls off.
 
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