filter simulation problem

[hoolish]

I have used one opamp and one out-chip capacitor and resistor to build the first order Butterworth low pass filter. The cutoff frequency is 10Hz. When I use function generator to input a sinawave at 3Hz. I can use osillscope to see clearly the input signal as the sinewave. But at the filter output, I can see the signal with a lot of noise. It is not a good sineware because the noise floor is very high. I want to know the reason. Please help me.

 

[flatulent]

Try making an inverting amplifier and see what the noise and gain and frequency response are. Make sure your are not overdriving the amplifier.

Your filter circuit should either be made with two equal value resistors in the inverting configuration with the capacitor across the output to the inverting input, or you should have a series R shunt C to the noniverting input and the output connected with a wire to the inverting input.