Electrolytic or ceramic capacitors? for specific filter applications

[UnknownFactor]

I am trying to make an amplification and filtering circuit, but I am a bit confused on which capacitor type to use on the different parts.

I want to include three different types of filters:

• a high pass filter with cutoff at 7Hz (link)

• a low pass filter with cutoff at 31 Hz (link)

• and a notch filter at 50 Hz (link for 60Hz)

I am not sure if the capacitors on the schematics are of the right type. I have read on the differences of the different capacitors but I fail to understand in which application each should be used.

What capacitor type would be better for each of the 3 filters above (ceramic/tantalum/electrolytic)? How important is it to pick the right capacitor type?

 

[KlausST]

How important is it to pick the right capacitor type?

Hi,

They won't influence frequency nor operation ..

But they will influence distortion, drift, size, cost...
Polarized capacitors usually are not useful for AC application unless they are biased with sufficient DC voltage.

Klaus

 

[danadakk]

Polly, Teflon, in general film....

https://eepower.com/capacitor-guide/types/film-capacitor/#

No to ceramics -

https://e2e.ti.com/blogs_/archives/b/precisionhub/posts/stress-induced-outbursts-microphonics-in-ceramic-capacitors-part-1

Regards, Dana.

 

[D.A.(Tony)Stewart]

Considering that I believe you have the wrong topology and values, the type of caps won't help. But scaling in order to use MLCC is often adequate and NP0 for high Q high f and e-caps with adequate bias should rarely get into an ESR issue to limit choices.

 

[danadakk]

Effect of capacitor type in an active filter circuit?

Below is a unity-gain low-pass filter implemented with a Sallen–Key topology: If C1 and C2 is large, are electrolytic capacitors recommended? Similarly, if C1 and C2 is small, are any type of cer...

electronics.stackexchange.com

https://www.x2y.com/publications/microphonics.pdf

Regards, Dana.

 

[UnknownFactor]

I should had also mentioned that the purpose of my project is to measure some 7-30Hz signals with amptitude 10-30 μV. The filters are to be used after an operation amplifier.

This is an hobby project (I am not a professional electronics designer). I guess I will start with something and see how the signals come out and do modifications after. I will, also, revisit the filters' designs.

Thank you all for your comments

 

[D.A.(Tony)Stewart]

You might want to consider better specs 1st then design then scale to low C high R values, so that film is practical and cost-effective. But never skip step 1. Your question was already at step 3.