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Help with Band-Pass-Filter

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Roger_NO

Member
Hi,

Im currently trying to design a bandpass filter for a microphone.
I have downloaded TI's FilterPro app, but after building the circuit the result was bad. There is no output and i have gone over the wiring to check if it is correct.

I am testing the filter with a signal generator wit the current output; 50ohm, 500mv p-p.

I am supplying the opamps with 5VDC.

Thanks.

PS. I am pretty new at filter design.
 

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hey, the only thing i can think of is that you have probably made a wiring mistake, check again thoroughly.If you have soldered the circuit, check for bad soldering connections..

most opamps require a +voltage and a -voltage to work correctly. check if that is fine...

all the best,
deepak
 

JimB

Super Moderator
Most Helpful Member
The 5v supply may be a bit low for your op-amp, but the main problem is that you are using a uni-polar supply (0v and 5v).
With that circuit configuration you need a bipolar supply (-5v 0v +5v), connect the 0v of the supply to the common 0v line of the circuit, (where the op-amp non-inverting inputs are connected), then connect the supply -5v to the op-amp -ve connections and the +5v to the op-amp +ve connections.

JimB
 

kmgarudadri

New Member
Hello,
1. As per the design seed value of R1 is 10 K. But you have used 4.7 K.
Any rason ?
2. How did you get the Value of R3 = 220 ??

3. How are you testing it ?
This being a narrow band - band pass filter are you testing with a sweep input ??

May be it's a testing problem

GKM
 

MikeMl

Well-Known Member
Most Helpful Member
As designed by FilterPro, the opamps expect split supplies. If you are running it on a single 5V supply, it will not work. You can offset the non-inverting inputs to a well bypassed midpoint on a voltage divider tied between Vdd and ground, and then capacitively couple the input signal into the first stage.
 
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