ADC Filtering Deep Dive

[@dymastro788]

Great video's Zach, also appreciate that you are answering questions from the comment section. Keep up the great work!

[@AltiumAcademy]

Glad you like them!

[@YoussefEl.]

Hi! Correct me if im wrong, but the non inverting opamp circuit will have a limited bandwidth on the "gained" portion of the input.. the gain is (1 + Zfb/Zin-), so the +1 term would bypass the filtering. Vout will be vin (no BW limit) + vin×gain (with RC Bandwidth limit) The non inverting input should also be filtered in order to match the BW of the feedback network

[@SeanPorio]

This is totally correct, if it’s possible it might be better to use two op-amps or a discrete buffer followed by another filter topology like a sallen-key to get the same effect if the input impedance is high and/or unknown (plus you can easily get a second pole and resonance to play with!)

[@hazehh789]

Question about mounting holes for RF circuits, for FR4 PCB, how do you calculate the maximum torque of the mounting screw in order not to deform the pcb hence changing its impedance?

[@Zachariah-Peterson]

Good question, I do not want to guess but it would be based on the modulus for the material. You have to do a lot of deformation to change the impedance, I think another important point is to find the right torque to help suppress vibration.

[@RedRacconKing]

Cutoff frequency is 7.23MHz

[@sergiolozano8621]

Thanks @Zachariah-Peterson for all your content. One question on the filtering stage: I've seen scenarios where the sample and hold switching of the ADC introduces noise that may couple back in the feedback loop of the previous amplification stage, before the ADC. How would you filter out this noise? Also with an RC? Cheers

[@Zachariah-Peterson]

Is this in reference to the case of an active filter with a high-impedance source? If this is fast switching noise that draws strong transients it might be exciting a pole in the amplifier's feedback loop. In that case I would expect a sinusoidal noise component, possibly with some additional distortion (harmonics). Is this what you're referring to?

[@AmitSharma-bm2qj]

Great

[@Bob-zg2zf]

you look so fit😉