Opamps bypassing inquiry

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#5
There are no ideal values. The bypass will depend upon the size and type of the elcos and if you are really serious it should be determined by listening. It seems that a combination of cap+resistor (snubber) often sounds better than just a cap bypass.
 
#6
there is an article on supply bypass caps in the May issue of AudioXpress -- and the answer (nonanswer?) is that sometimes 100nF is better than 470nF --

however, ceramics have a very good place in reducing RFI on power pins due to their low ESR/ESL compared to film caps.
 
#8
I don't really think that they screw up the sound as bypass elements. You can measure the distortion in using them as coupling caps, however.

In using an opamp for measurement, using a high bandwidth current feedback amp etc. you might want to compound the sin and add a 4.7uF or 6.8 uF tantalum in parallel !
 
#9
They often do screw up the sound when used as bypass caps. I have tried this a lot and don't use ceramic caps anymore for bypassing. My experience is with standard ceramic and Kemet X7R multilayer caps. One good electrolytic cap per rail and one 100 nF film cap from + to - on the opamps supply pins is what I use mostly. Key is to use all three caps as close to the pins as possible for optimal results.

In clock circuits and other RF related schematics ceramic caps are needed because of their RF characteristics.
 
#11
This is a bit off topic but the CS8412 has an analog grnd pin. Should this be connected to the digital grd or the analog grnd? Doesn't this receiver chip work with digital signal only? Why there is an analog grnd pin?

I have run separate ground plane for digital and analog section in my DAC. I connected the two near the main power supply capacitors. It this good or bad?
 
#12
quantran said:
This is a bit off topic but the CS8412 has an analog grnd pin. Should this be connected to the digital grd or the analog grnd? Doesn't this receiver chip work with digital signal only? Why there is an analog grnd pin?

I have run separate ground plane for digital and analog section in my DAC. I connected the two near the main power supply capacitors. It this good or bad?
Click to expand...

Hi

http://www.tentlabs.com/Info/Articles/Supply_decoupling.pdf

remember, currents run in circles......

cheers
 
#16
Ok so how do you do the bypass to ground on opamps which dont have a ground on them just +V and -V. Do you literaly just run a cable all the way around the board to the ground plane. Pr can i use one of the NC pins on the chip and use this to get to the back side of the board and them run a wire from this solder point to gorund?

I guess the really question i am asking is is it ok to connect something to the no connect pins of a chip so i can take the ground through the leg to the other side of the board where the ground plane is?

Any help gratefully received.

Also for by-passing my ad825 what would seem like a good set up i have got to hand 1uf, 0.1uf and0.01uf Wima's. Would these be any good and in what cobimeation. also have some backgate 100uf but i guess these are too big for by-pass application


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