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Analod ground, Digital ground and Earth

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yousaf_madni

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Can anybody plz tell me the difference b/w Analog ground, digital ground and earth. If somebody has any reference or help file, I will be obliged. Thanx
 

Earth is what you stand on outdoors. This ground is necessary for electrical safety from the mains. How you connect to it is described in detail by the safety laws in each countries.

Analog ground is the reference point for analog circuits. This also is the power return point.

Digital ground is the reference point for digital circuits. This also is the power return point.

Where problems occur is when the ground is not a true conductor. Return circuit currents flowing through it cause voltage differences between different physical points. When circuits use these different points for their circuit ground, their outputs relative to other ground points are not the same.
 

it's a matter of convenience. It's better to tie all your analog returns by one side (analog ground), all your digital retuns by another side (digital ground). Eventually does exist a third common conection, namely chassis o "earth" which is connected to real ground (the planet). It's for safety and sometimes it helps to damp noise (some times it puts noise in your circuit).
Where do you tie digital and analog ground?, one solution is in a node close to the power supply. But is your circuit includes RF that may be not a good choice.

To summarize: there is no easy answer. To deal with grounds and earths is a tricky subject and the best solution is a function of your system.

A nice book is HW Ott, Noise Reduction Techniques in Electronic Systems. https://www.ewh.ieee.org/r4/se_michigan/emcs/HenryOtt2005.htm

Some time ago that book was available in the WWW and today still seems to be available at Elektroda:

See this answers to people who dealed with your doubts:
 

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