Looking for design help for very low frequency active low pass filter. Cut off at 0.1Hz, 2 pole with a Q of 0.5 will be good. Any guidance wil be appreciated.
All continuous time op amps have a 1/f noise corner. Depending on the technology (bipolar, JFET, CMOS),
the corner will be between 3 Hz and 10 kHz. The autozero parts do not have a 1/f corner, but generally
have higher noise. However, we do have the ADA4528-1 which is a recent part with less than 6 nV/rt-Hz,
so I would use two and build an SK or MFB filters. Also keep your resistor values low so you don't
add much thermal noise.
Thanks for the quick respsonse Harry.
We are using a SK filter as indicated in your circuit note CN0127.
While the device selection was signiifcant guidance, what is the suggested (dielectric) type of capacitor that we should use to lower the noise floor. This is particularly a concern where the size has to be small and the cut off is as low as 0.1Hz (points to almost 100uF in a chosen configuration).
The resistors chosen are metal film.
Anand C J
Sorry, I know nothing about capacitor noise.
Thanks for the respsonse Harry, Anand C J
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