hoolish
Newbie level 6
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.