hello all
working on a circuit to glow an led on whenever the input signal frequency is between 970hz to 1030hz.
but the problem is the amplitude of the input signal which can be anywhere between 1<=A<=4.
i used a bandpass filter to filter the signal for designated frequencies but after that i used a comparator but i cant use a single reference voltage in that because for every single amplitude the output voltage changes.
any suggestions ?
Thanks

 

You already have a signal of the appropriate frequency at the filter output. Why not just amplify that up to or beyond amp clipping level and drive the LED from the amp output (perhaps via a diode/cap integrator)?

 

Look at an LM567 chip.

 

@mikeML
the only components i have to use are lm741 or lm747
and resistors , capacitors, diodes..
@alec t
just have a look on the attached schematic snapshot.
Thanks

 

Sounds like a school assignment. If so, how come it is not in the homework forum..

Your required Q is f/Δf = 1000/(1030-970) = 17. That will take a much different filter...

Your filter is way too simplistic. To get such a narrow frequency response, you will need a much sharper bandpass filter.