Problem with signal output of second order LPF

[Willykilly]

second order lpf

I designed a low pass filter as per the circuit given in
https://www.sensorsmag.com/da-contr...rder-anti-aliasing-filter-a-sensor-signa-5861

but the signal output is not coming correctly. For a sine wave input it gives out 3/4 of positive half correctly but the negative half of the sine wave is distorted and I do not know what shape is that. What could be the problem. I am using exact vales of components and I asked my friend to verify the connections after verifying the connections myself.

Thanks in advance.

 

[flatulent]

Re: second order lpf

It looks like your signal is a higher amplitude that the power supplies to the op amp an it is clipping. Either that or your op amp has a limited output swing. Try using one with "rail to rail" output ability.

 

[LvW]

Re: second order lpf

Willykilly,

you didn't say anything about the power supply : single or dual?

 

[Willykilly]

Re: second order lpf

I was using a quad channel opamp, with single power supply (LM399).

Thanks in advance.

 

[keith1200rs]

second order lpf

Most likely you haven't biased it correctly for single supply operation. Please post your actual circuit.

Keith

 

[LvW]

Re: second order lpf

I was using a quad channel opamp, with single power supply (LM399).

Thanks in advance.

Yes, and this is the reason for your problems (most probably).
Or did you install any biasing network (which is necessary for single supply)?