Opamp decoupling schemes [& Better grounding]

[kaushama]

For my next preamp project I will be using OPA 2134. For fast opamps the decoupling method is very crucial to reduce noise.

There are several ways of decoupling schemes. What is the best method of bypassing opamps? [See Figure]

I plan to have a separate ground plane for decoupling as it is better to keep the high frequency noise away from the signal paths.

What are the optimal values for C1 and C2? For C1 ceramic is the best type. For C2 what is the best type?

Hope this will serve as a good FAQ thread for decoupling methods!

[abid_rehan]

Some people prefer to use different ground planes for signal path and supply grounds, some use star ground topology, some use same ground for both.
It will depend how it works out for you, as i had mentioned in some of the post its d b better to have a look at analog website and Texas Instruments website, they have got some good data about grounding techniques for single and dual supply operations.

[kaushama]

Thanks! I will put all the links I can find here too. Idea is to get a sort of complete faq for the decooupling techniques.

Out of the schemes outlined what is the better method of capacitor topology?

[DSP_Geek]

Originally posted by kaushama
Out of the schemes outlined what is the better method of capacitor topology?

I use the last scheme, with 100 nf ceramics bypassing generic 33 uf 25 V electrolytics. Works well so far on the 2134s in my system.


Francois.

[Calimero]

What also might be interseted to know with respect to decoupling of opamps, is if decoupling between + and - supplies or +-gnd and - and gnd is preferred.

I experienced (on advice of Pedja) that the last scheme work much better for bipolar-opamps (like lm6171).

Regards Henk

[Christer]

Originally posted by Calimero
What also might be interseted to know with respect to decoupling of opamps, is if decoupling between + and - supplies or +-gnd and - and gnd is preferred.

It depends on the internal design of the op amp.
http://www.analog.com/UploadedFiles/...8865AN-202.pdf