Selecting Frequency Range only at 25 KHz

I want to allow only the Frequency range of 25 khz from a mic input , so the remaining sound ( remaining frequency ) should get eliminated. How to make this possible ? Will Band pass filter can give solution to this ? If so plz design it to select only the frequency range of 25 khz.

See here:
"http://www.wa4dsy.com/robot/active-filter-calc(OpAmp filters calculator)":http://www.wa4dsy.com/robot/active-filter-calc

This one is too easy, 1st you have a zero, that is a cap input with a resistor connected to that and then to ground. The connection node then can be followed by a buffer amp, that feeds a resistor with a cap connected to the resistor then to ground. The R/C connection node is the output. unbuffered. Both resistors and caps are the same value. So lets say you start with a 10K resistor, the cap value is 640 pF.

Now since you gave zero, as in nothing, as in blank paper, additional info, the arbitrary choosing of the R as 10K may or may no work but the R/C product will be the same if you have to choose a different resistor. That would be 6.40*E-6.

I will not draw a schematic for this because too simple. Note there are many many ways to get a leading zero followed by a trailing pole circuit, especially if you use an op amp.

I should say the 6/40*E-6 is the resistor value multiplied by the cap value, which is constant for 25KHz.

Your possibly looking for a notch filter or a bandpass filter or combination of both with a very high Q

See link below
http://www.radio-electronics.com/info/circuits/opamp_notch_filter/opamp_notch_filter.php


http://www.radio-electronics.com/info/circuit...mp_band_pass_filter/op_amp_bandpassfilter.php

Quickly doing some research produces these answers from maxim semiconductors for programable filters which for your purposes will produce far more accurate results and I would think maybe easier for you to use

See this link for more details

http://www.maximintegrated.com/datasheet/inde...1j2j0j1.4.0.les%253B..0.0...1ac.1.sQW-L20FNdQ

Mark, a programable notch filter? The kid need to learn basic electronics 1st. He/she need the fundamentals of at leat the 1st week in college.

A programable notch filter, seriously.

Beg your pardon earl I didnt notice that, my mistake, Although I have given three possibilities and the notes are there in full

There is also no mention of how many weeks of college that the questionare has attended

So my comments havent been out of touch to be honest, we are also looking at a digital age now where we do need to move and change the subjects slightly to suit modern demands


It isnt really that difficult to understand

Read the analogue methods first then migrate to digital interpretation

In fact if anything they should be learning this anyway otherwise what they are learning wont be much use when it comes to having to sit down and produce a design for a prospective employer

Come out with an analogue design at that stage I think they might just sit there and laugh at you

Put another way Earl not whishing you to take this personally which I trust you wont Exactly how many class AB amplifiers do you see on the market these days Not many thats because the majority are class D with mpeg decoders and bluetooth usb front ends or dsp front ends

Ill quantify this just a little more for you Last week I went to visit a company for future possible employement The modern CD changers no longer have hardwire bus control They cost the end user some 3000 pounds stirling to replace The bus and audio interfaces btw controlling head unit and CD changer digital tv and tuner plus car brain all interlink via digital communication services, protocols They are no longer analalogue waveforms which you can readily scope as you would have some 10,15 years ago The technology is that advanced they use fibre optics to link the equipment for both signalling and control

Do you honestly believe that showing people how to build an analogue bandpass filter, notch filter is going to solve the difficulties industry is facing now

I dont think so somehow I dont think that you would survive for less than five minutes in bussiness or do you think otherwise

What you going to do keep people ten years behind while the market advances even more or are you going to attempt to move people into modern day electronics so that they are ready to compete in the modern world

Again which is it to be Earl Do you want your futures to be competetive and to be leaders or will you just be happy to be second best all the time

Be serious Uhm yes Earl Im afraid I am being very serious That is exactley what they have learn Im no expert but I know failure when I see it I also know that if I were any serious student wanting to learn I would demand the best knowledge not second best and as a former student still am Id be demanding and wanting to know why my tutors are not teaching me the required technology that I need to gain employment In fact id be bloody annoyed about it