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Supply noise and ground noise effect in analog circuits

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Dhivi

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Hi,

Can anyone please tell me that which noise i.e supply noise or ground noise will be more in analog circuits and why?


Thanks in advance
Dhivi
 

Hi,

It depends. If your power supply decoupling is not proper then there will be chances of supply noise and if Grounding is not proper, then ground noise may come into picture.

It depends on how well is your design.


Amit
 

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It depends upon the circuit, the decoupling used, the noise sources, and the circuit layout.
There's no single answer to your question.
 

Ground noise is probably worse, because ground is often a
reference for "single ended" signals that are really processed
differentially, so subject to gain rather than designed
attenuation (as supplies see, PSRR). The problem is worse
when you are not dealing with "a" ground, but a ground
network with various series and shunt elements and noise
injected at different points (i.e. reality).

Differential (explicitly) signals remove much of the ground
sensitivity leaving only CMRR / PSRR attenuated ground
"input".
 
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    Dhivi

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Thank you for your response dick and crutschow.

we can control or reduce supply noise by adding proper decap right, but if ground noise is worse means Is there any way to reduce that one?
 

Hi,

For reducing ground noise, you should follow guidelines while designing layout. There are plenty of them available online.

Amit
 

Hi,

If you have a circuit in mind you should show us, so we can give detailed help.

Suppress GND noise
* differential wiring, as said before
* R or L in the signal line between noisy and clean GND planes, C to target GND.
* difference amplifiers
* intelligent GND_splits and GND_joints to make all involved GND to a clean GND.

Klaus
 

The golden rule is to have a ground system through which no current ever flows.
Then you need a power return system that does carry all the noise current which is kept separate.

The ground system then becomes a zero noise reference with respect to all the analog signals, and because no current flows, there cannot be any relative voltage drops, and no introduced noise.

The reference ground needs to be tied to the power ground, but at one point only. Where best to do that depends on the type of circuit.
 

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