help on how to design a notch filter with band reject frequency of 20khz

 

How much attenuation at the bottom of the notch?
How steep are the skirts?
How much ripple is acceptable in the passband?
Active or Passive?
How much power do you need to handle?
What is the purpose?

 

You have this tool. You will have to register but nothing more than that.
http://www.ti.com/ww/en/analog/webench/webench_filters.shtml

 

10 character minimum.

 

its a 20khz active notch filter design witha reasonable attunuation level compared to the passband frequency.

 

could not register

 

There is also a desktop version:
http://www.ti.com/tool/filterpro

Registration on TI's site should work flawlessly.

 

I do not respond to email requests. I answer in the open forum.
The help you seek can be obtained via a Google search for "Active Notch Filters". The first five hits have pretty much everything you need.

You still have not articulated your requirements. Is that because you don't have any requirements laid out? I'm just asking.

 

was not given any specification,all that was given was the 20khz to be rejected. its the first time am working on this, thats why i need help on it. the calculations of resistors and capacitors using the frequency given. want to use the fliege notch topology.

 

So follow one of the articles and show us what you get. In real life any manager who gave you such an assignment without requirements would be considered incompetent and a prime candidate for being sacked.

 

would do just dat

 

this is what i got after simulating

 

morning all, i breadboarded and sent a 20khz signal through my circuit from the oscilloscope it looks as if the signal was not there(like thiny ripples) but after calculations found out that the output signal was 16.67khz. Is that ok?

 

morning all, i breadboarded and sent a 20khz signal through my circuit from the oscilloscope it looks as if the signal was not there(like thiny ripples) but after calculations found out that the output signal was 16.67khz. Is that ok?

If the input was 20kHz the output should be at the same frequency albeit at significantly reduced magnitude. Looking at your earlier post with your proposed circuit design - it does not appear to comply with the arrangement shown here

http://earmark.net/gesr/opamp/notch.htm

for instance.

I would also suggest choosing a different op-amp and using bipolar supply for the op-amps. The amplifier bandwidth is quite critical to the outcome with respect to notch depth.

 

You cannot operate a 741 op amp from a single supply without biasing the inputs at 1/2 the supply voltage. Even then it's unlikely to operate properly with only 6V.

If you want to operate from a single supply it would be best to use an op amp designed for single supply operation such as the rail-to-rail types. But even then you need to bias the input at 1/2 the supply voltage for AC signal input.

 

thanks alot sir. trying to understand the function of various component in the fliege notch topology. any book or link to help me in understanding the role they play

 

A 741 opamp is 44 years old, works poorly or does not work with a supply below 10V and operates poorly above 9kHz.

You need an opamp that works well at 100kHz or higher.

You need to learn about how to bias the input of an opamp that has a single-polarity supply since you have the input at 0V where the input does not work.