Electronics > Beginners
Why aren’t bypass capacitors built into IC’s?
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danielbriggs:
Hi all,
After watching Dave’s excellent couple of videos about bypass capacitors... I was left wondering the question “why aren’t bypass / decoupling capacitors built into the IC package if they’re needed for optimal operation?
They’d be super close to the die, so that would be a good thing?

Is it just space and cost issues preventing this? Or are there any better reasons for this not being the norm.

Thanks,
Daniel
coppice:
It is unusual to put decoupling caps inside the IC package, but decoupling caps on the outside of the package are fairly common for high performance parts.
Zero999:
I believe this question has been asked here before, but can't find it.

It's because there isn't space in the package and it's just cheaper to put them in externally.

EDIT:
It's been asked on Stack Exchange, which Google shows on the first hit. I don't know about here.
https://www.google.com/search?q=Why+aren%E2%80%99t+bypass+capacitors+built+into+IC%E2%80%99s%3F&ie=utf-8&oe=utf-8&client=firefox-b
David Hess:
Sometimes decoupling or other capacitors are added inside the IC package either on the IC or on the lead frame but it is usually more economical to require them externally.
KE5FX:
It's becoming more common to see caps inside IC packages.  They are not always mentioned in the data sheet, but they can be 'found' if you look. 

E.g., here's a nice shot of a switching regulator (LT8650S) with both input- and output-side bypassing:



And a clock synthesizer chip (LMK61E2):



They are present in FPGAs too in some cases (Kintex for sure, and presumably Virtex).  I wouldn't be surprised if they're used in SoCs and SDRAM parts as well. 
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