Hey everyone. I'm learning electronics and during this process I'm looking at some board schematics and doing a few designs myself jsut to get the heng of it.

I came across the following schematic. My doubt is, why are there 2 capacitors C7 and C8 , one with 10uF and one with 1uF ? They are both uF, correct? Could there not be just one capacitor?

 

The usual reason for this is that large value capacitors work best for low frequencies and small values work best for high frequencies.
This document is a godd discussion of the whys and wherefores of bypass capacitors.
https://www.intersil.com/content/dam/Intersil/documents/an13/an1325.pdf

 

Did they call out the 1 uF as MLCC ? They have excellent higher frequency
performance.

Regards, Dana.

 

Seems like you could remove C8 and keep C7. C7 should be tantalum. Add a 0.01uf cap to pin 4 to keep noise down.

Also looks like the ENA pin isn’t wired correctly if it’s supposed to delay the output.
Vbat/Bus is shorted to GND when V+ is applied to C6.

eT

 

Thank you all so much for the replies !

 

why are there 2 capacitors C7 and C8 , one with 10uF and one with 1uF ? They are both uF, correct? Could there not be just one capacitor?

where can you buy an 11uF capacitor???

 

You can buy it at Mouser.

The question was mostly theoretical, if we could use one capacitor instead of 2 , or was there a specific reason to use two capacitors?

From the answers before, what I gathered is that two capacitors are being used because : one is better suited for clear signal noise of lower frequencies and the other for higher frequencies, and not because it is required 11uF capacitance per ce.

Are you suggesting that the decision for 2 cap 10uF + 1uF is because of lack of availability of 11uF and not a technical reason?

 

You can buy it at Mouser.

Are you suggesting that the decision for 2 cap 10uF + 1uF is because of lack of availability of 11uF and not a technical reason?

I can't see what technical reason there could be , the circuit will just see one cap 11uF ... post 2 makes no sense to me.

I have never seen an 11uF capacitor .... like resistors, not all values are manufactured . If a circuit requires a very specific value , then two have to be put in series /parallel to make the required resistance or capacitance.

It seems the circuit diagram indicates these are all electrolytic , the -ve terminal appears to be marked ???

Not even clear that these caps are 10uF and 1 uF ...why are the 'u' s different???

 

I can't see what technical reason there could be , the circuit will just see one cap 11uF ... post 2 makes no sense to me.

Follow the link in post #2. That will explain why even capacitors of the same value are not necessarily interchangeable.

 

Follow the link in post #2. That will explain why even capacitors of the same value are not necessarily interchangeable.

I did follow the link ... but what be the effect if two different types are in parallel ...

Are these 1uF and 10uF ??? why are the 'u's different ??? are they electolytic ??why the -ve sign ??

 

The reason the "u"s are different escapes me.

This is the product where that schematic comes from, in case it helps :
https://learn.adafruit.com/adafruit-feather-32u4-basic-proto/overview

 

the u and μ symbols are used interchengably to mark SI prefix micro (10^-6) and in the cricuit they mean the same thing. But it is nice to be consisitent and to use only one of those, preferably u because there will be less issues with incompatible fonts etc.